Fix various typos

Mainly fix typos in comments, but also some minor code changes:

* Rename `apply_on_poiner` to `apply_on_pointer`.
* Rename `ImeState::Commited` to `ImeState::Committed`
* Correct `cfg_attr` usage: `wayland_platfrom` -> `wayland_platform`.

src/platform_impl/linux/wayland/seat/mod.rs

@@ -54,7 +54,7 @@ pub struct WinitSeatState {
     /// The current modifiers state on the seat.
     modifiers: ModifiersState,
 
-    /// Wether we have pending modifiers.
+    /// Whether we have pending modifiers.
     modifiers_pending: bool,
 }