Implement Helix Support (WIP) (#19175)

Closes #4642 

- Added the ability to switch to helix normal mode, with an additional
helix visual mode.
- <kbd>ctrl</kbd><kbd>h</kbd> from Insert mode goes to Helix Normal
mode. <kbd> i </kbd> and <kbd> a </kbd> to go back.
- Need to find a way to perform the helix normal mode selection with
<kbd> w </kbd>, <kbd>e </kbd>, <kbd> b </kbd> as a first step. Need to
figure out how the mode will interoperate with the VIM mode as the new
additions are in the same crate.

crates/vim/src/motion.rs

@@ -529,6 +529,8 @@ impl Vim {
                         return;
                     }
                 }
+
+                Mode::HelixNormal => {}
             }
         }
 
@@ -558,6 +560,8 @@ impl Vim {
             Mode::Visual | Mode::VisualLine | Mode::VisualBlock => {
                 self.visual_motion(motion.clone(), count, cx)
             }
+
+            Mode::HelixNormal => self.helix_normal_motion(motion.clone(), count, cx),
         }
         self.clear_operator(cx);
         if let Some(operator) = waiting_operator {