[build] [web] Fix (missing) examples compilation for PLATFORM_WEB

[asdqwe]

Error logs:

~/raylib-master/src$ make PLATFORM=PLATFORM_WEB
[...]
~/raylib-master/src$ cd ../examples/

~/raylib-master/examples$ make PLATFORM=PLATFORM_WEB core
[...]
core/core_basic_window_web.c:18:10: fatal error: 'raylib.h' file not found
   18 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]
core/core_input_virtual_controls.c:18:10: fatal error: 'raylib.h' file not found
   18 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]

~/raylib-master/examples$ make PLATFORM=PLATFORM_WEB textures
[...]
textures/textures_image_channel.c:18:10: fatal error: 'raylib.h' file not found
   18 | #include <raylib.h>
      |          ^~~~~~~~~~
1 error generated.
[...]

~/raylib-master/examples$ make PLATFORM=PLATFORM_WEB models
[...]
models/models_bone_socket.c:16:10: fatal error: 'raylib.h' file not found
   16 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]
models/models_point_rendering.c:16:10: fatal error: 'raylib.h' file not found
   16 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]

~/raylib-master/examples$ make PLATFORM=PLATFORM_WEB shaders
[...]
shaders/shaders_basic_pbr.c:20:10: fatal error: 'raylib.h' file not found
   20 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]
shaders/shaders_shadowmap.c:14:10: fatal error: 'raylib.h' file not found
   14 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]
shaders/shaders_vertex_displacement.c:16:10: fatal error: 'raylib.h' file not found
   16 | #include "raylib.h"
      |          ^~~~~~~~~~
1 error generated.
[...]

Also fixes #4483

[raysan5]

@asdqwe thank you very much for reviewing this issue! 👍🙂