feat(language): derive Clone and Copy on LanguageFn

Allows a LanguageFn to be passed around and create multiple languages since Language::new consumes a LanguageFn

LanguageFn just wraps a function pointer, which already conforms to Copy so this is a simple addition.

lib/language/language.rs

@@ -1,6 +1,7 @@
 #![no_std]
 /// LanguageFn wraps a C function that returns a pointer to a tree-sitter grammer.
 #[repr(transparent)]
+#[derive(Clone, Copy)]
 pub struct LanguageFn(unsafe extern "C" fn() -> *const ());
 
 impl LanguageFn {