Enable x11 feature by default in processing_pyo3

The workspace Cargo.toml already enables x11 by default, but
processing_pyo3 has its own default features that didn't include x11.
This meant building with maturin from the sub-crate would produce a
Wayland-only wheel even on X11 systems.

Add x11 to processing_pyo3's default features to match the workspace.

Author: pepc84

crates/processing_pyo3/Cargo.toml

@@ -11,7 +11,7 @@ name = "mewnala"
 crate-type = ["cdylib"]
 
 [features]
-default = ["wayland", "static-link"]
+default = ["wayland", "x11", "static-link"]
 wayland = ["processing/wayland", "processing_glfw/wayland"]
 static-link = ["processing_glfw/static-link"]
 x11 = ["processing/x11", "processing_glfw/x11"]