parser: Make `KeyboardKey` private

Get rid of these warnings:

    warning: private type `parser::Character` in public interface (error E0446)
      --> src/parser.rs:72:15
       |
    72 |     Character(Character),
       |               ^^^^^^^^^
       |
       = note: #[warn(private_in_public)] on by default
       = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
       = note: for more information, see issue #34537 <https://github.com/rust-lang/rust/issues/34537>

    warning: private type `parser::KeyCode` in public interface (error E0446)
      --> src/parser.rs:73:13
       |
    73 |     KeyCode(KeyCode),
       |             ^^^^^^^
       |
       = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
       = note: for more information, see issue #34537 <https://github.com/rust-lang/rust/issues/34537>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/parser.rs b/src/parser.rs
index 6f7f98e..9bbdede 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -68,7 +68,7 @@ impl KeyCode {
 }
 
 #[derive(Debug, PartialEq)]
-pub enum KeyboardKey {
+enum KeyboardKey {
     Character(Character),
     KeyCode(KeyCode),
     NXKey(NXKey),