Add multiplayer-bomber example

[Yarwin]

closes: #903
A demo adapted from: https://github.com/godotengine/godot-demo-projects/tree/master/networking/multiplayer_bomber

I took few liberties, mostly related to caching references to nodes in the scene tree by using OnReady, using signals instead of parsing tree in process, and declaring gamestate autoload as engine singleton but it is mostly faithful to the original example – including one bug (errors when host disconnects before the peer).

I changed few assets, since I was unable to find their original sources with the license. All the other assets (explosion and shard) not explicitly listed in example's README.md has been created for this particular example by godot's contributors.

[julianbolts]

[**Multiplayer bomber**](multiplayer-bomber)

please update the path here 🍻

[Bromeon]

Fixed CI in master and rebased this PR.

I'll likely do some other improvements on master, also regarding newer APIs in dodge-the-creeps.

[ValorZard]

got error when trying to build

C:\github\demo-projects>cargo build
    Updating git repository `https://github.com/godot-rust/gdext.git`
    Updating crates.io index
    Updating git repository `https://github.com/godot-rust/godot4-prebuilt`
     Locking 32 packages to latest compatible versions
      Adding rand v0.8.5 (available: v0.9.0)
  Downloaded heck v0.5.0
  Downloaded nanoserde-derive v0.1.22
  Downloaded ppv-lite86 v0.2.21
  Downloaded unicode-ident v1.0.18
  Downloaded venial v0.6.1
  Downloaded proc-macro2 v1.0.94
  Downloaded quote v1.0.40
  Downloaded nanoserde v0.1.37
  Downloaded zerocopy v0.8.24
  Downloaded glam v0.28.0
  Downloaded libc v0.2.171
  Downloaded 11 crates (1.7 MB) in 0.77s
   Compiling godot-bindings v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling gdextension-api v0.2.2 (https://github.com/godot-rust/godot4-prebuilt?branch=releases#09432b4c)
   Compiling proc-macro2 v1.0.94
   Compiling unicode-ident v1.0.18
   Compiling regex-syntax v0.8.5
   Compiling nanoserde-derive v0.1.22
   Compiling heck v0.5.0
   Compiling zerocopy v0.8.24
   Compiling godot-cell v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling glam v0.28.0
   Compiling cfg-if v1.0.0
   Compiling getrandom v0.2.15
   Compiling rand_core v0.6.4
   Compiling nanoserde v0.1.37
   Compiling regex-automata v0.4.9
   Compiling godot-codegen v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling godot-macros v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling quote v1.0.40
   Compiling venial v0.6.1
   Compiling ppv-lite86 v0.2.21
   Compiling regex v1.11.1
   Compiling rand_chacha v0.3.1
   Compiling rand v0.8.5
   Compiling godot-ffi v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling godot-core v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling godot v0.2.4 (https://github.com/godot-rust/gdext.git#6e210240)
   Compiling dodge-the-creeps v0.1.0 (C:\github\demo-projects\dodge-the-creeps\rust)
   Compiling multiplayer-bomber v0.1.0 (C:\github\demo-projects\multiplayer-bomber\rust)
   Compiling hot-reload v0.1.0 (C:\github\demo-projects\hot-reload\rust)
error[E0412]: cannot find type `AudioStreamPlayer` in this scope
  --> dodge-the-creeps\rust\src\main_scene.rs:17:22
   |
17 |     music: Option<Gd<AudioStreamPlayer>>,
   |                      ^^^^^^^^^^^^^^^^^ not found in this scope
   |
help: consider importing this struct
   |
1  + use godot::classes::AudioStreamPlayer;
   |

error[E0412]: cannot find type `AudioStreamPlayer` in this scope
  --> dodge-the-creeps\rust\src\main_scene.rs:18:28
   |
18 |     death_sound: Option<Gd<AudioStreamPlayer>>,
   |                            ^^^^^^^^^^^^^^^^^ not found in this scope
   |
help: consider importing this struct
   |
1  + use godot::classes::AudioStreamPlayer;
   |

error[E0412]: cannot find type `AudioStreamPlayer` in this scope
   --> dodge-the-creeps\rust\src\main_scene.rs:109:33
    |
109 |     fn music(&mut self) -> &mut AudioStreamPlayer {
    |                                 ^^^^^^^^^^^^^^^^^ not found in this scope
    |
help: consider importing this struct
    |
1   + use godot::classes::AudioStreamPlayer;
    |

error[E0412]: cannot find type `AudioStreamPlayer` in this scope
   --> dodge-the-creeps\rust\src\main_scene.rs:113:39
    |
113 |     fn death_sound(&mut self) -> &mut AudioStreamPlayer {
    |                                       ^^^^^^^^^^^^^^^^^ not found in this scope
    |
help: consider importing this struct
    |
1   + use godot::classes::AudioStreamPlayer;
    |

error[E0433]: failed to resolve: use of undeclared type `Input`
  --> dodge-the-creeps\rust\src\player.rs:67:21
   |
67 |         let input = Input::singleton();
   |                     ^^^^^ use of undeclared type `Input`
   |
help: consider importing this struct
   |
1  + use godot::classes::Input;
   |

error[E0433]: failed to resolve: use of undeclared type `Input`
  --> multiplayer-bomber\rust\src\inputs.rs:24:23
   |
24 |         self.motion = Input::singleton().get_vector(
   |                       ^^^^^ use of undeclared type `Input`
   |
help: consider importing this struct
   |
8  + use godot::classes::Input;
   |

error[E0433]: failed to resolve: use of undeclared type `Input`
  --> multiplayer-bomber\rust\src\inputs.rs:30:24
   |
30 |         self.bombing = Input::singleton().is_action_pressed(ACTION_SET_BOMB);
   |                        ^^^^^ use of undeclared type `Input`
   |
help: consider importing this struct
   |
8  + use godot::classes::Input;
   |

Some errors have detailed explanations: E0412, E0433.
For more information about an error, try `rustc --explain E0412`.
error: could not compile `dodge-the-creeps` (lib) due to 5 previous errors
warning: build failed, waiting for other jobs to finish...
For more information about this error, try `rustc --explain E0433`.
error: could not compile `multiplayer-bomber` (lib) due to 2 previous errors

C:\github\demo-projects>