First pass at implementing configurable read timeout for X11

[jasonterando]

Proposed solution for issue documented in issue 45.

[ChurchTao]

@jasonterando
Please take care of the formatting issues here and run basic fmt and clippy, otherwise the merged ci will not pass.

[ChurchTao]

@jasonterando
I modified a few #[cfg(target_os = "linux")] and the test passed. However, Linux does not have a CI test. Could you please run the test on a Linux machine? To ensure that everything is safe.

[jasonterando]

I think we're good (running on Linux Mint / Ubuntu)...

$:~/projects/personal/clipboard-rs$ cargo run --example image
   Compiling clipboard-rs v0.2.0 (/home/jason/projects/personal/clipboard-rs)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 4.73s
     Running `target/debug/examples/image`
["image/png", "image/jpeg", "image/avif", "image/bmp", "image/x-bmp", "image/x-MS-bmp", "image/x-icon", "image/x-ico", "image/x-win-bitmap", "image/vnd.microsoft.icon", "application/ico", "image/ico", "image/icon", "text/ico", "image/jxl", "image/tiff", "image/webp", "audio/x-riff"]
$:~/projects/personal/clipboard-rs$ cargo test
   Compiling clipboard-rs v0.2.0 (/home/jason/projects/personal/clipboard-rs)
    Finished `test` profile [unoptimized + debuginfo] target(s) in 4.17s
     Running unittests src/lib.rs (target/debug/deps/clipboard_rs-b98f79e4aeb98b3d)

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

     Running tests/file_test.rs (target/debug/deps/file_test-7316e766406a54db)

running 1 test
test test_file ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.36s

     Running tests/image_test.rs (target/debug/deps/image_test-dd5e132e5a66ba70)

running 1 test
test test_image ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.85s

     Running tests/string_test.rs (target/debug/deps/string_test-2741cf6cc92c3633)

running 1 test
test test_string ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.72s

   Doc-tests clipboard_rs

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

$:~/projects/personal/clipboard-rs$