feat: add feature "fancy-no-syscall" for wasm targets

[Boshen]

• closes Compile to wasm32-unknown-unknown / Compile without terminal_size #346
• closes fix(handler): do not call supports_color::on when color is forced #326

I added

• fancy-base feature to enable exports for the fancy feature
• fancy-no-syscall feature to disable all syscalls
• a wasm ci check to ensure future changes.

target_family = "wasm" will not work in this case because terminal_size will not compile under wasm32-unknown-unknown, the dependency has to be excluded.

[Boshen]

Thank you! I'll test this in my project tomorrow, let's make a release after I've confirmed the fancy features works on all systems.

[Boshen]

I have verified both features fancy-no-syscall and fancy-no-backtrace are working as intended.

[Boshen]

@zkat A new release would be greatly appreciated 🤝

[zkat]

@Boshen done. Should be out in 7.2.0 now.