feat: add more vim keybinds

This is a combination of 6 commits.

- added a new command
- change dd to use cut
- add prototypes for A I o O commands
- fixed keybind test compilation bug
- add keybinds for the new enter_mode commands
- added prototype for copy line

src/command.zig

@@ -43,7 +43,9 @@ pub fn Closure(comptime T: type) type {
         f: FunT,
         data: T,
 
+        ///The type signature of commands
         const FunT: type = *const fn (T, ctx: Context) Result;
+
         const Self = @This();
 
         pub fn init(f: FunT, data: T, name: []const u8, meta: Metadata) Self {