Fix X11 support and add floating window hint for tiling WMs

[pepc84]

Problem

mewnala crashes on X11 systems with GLFW Error: Wayland: Platform not initialized even when building from source with --features x11.

Root cause

The x11 feature in processing_pyo3/Cargo.toml was only passing it to processing but not to processing_glfw, so GLFW never actually got built with X11 support.

What I changed

• processing_pyo3/Cargo.toml : added processing_glfw/x11 to the x11 feature
• processing_glfw/Cargo.toml : added the x11 crate as an optional dependency
• processing_glfw/src/lib.rs : set _NET_WM_WINDOW_TYPE_DIALOG on X11 so tiling WMs like i3 and sway automatically float the window instead of tiling it

Note

X11 users still need to build with --no-default-features --features x11,static-link for now. Wayland is still the default.

Tested on

Arch Linux, i3/X11, AMD Radeon RX 6600 XT

[tychedelia]

We should probably guard with glfw.get_platform but this only matters for people compiling with x11 on wayland so not a big issue. Thanks!