Add initial vim mode mode switching

Co-authored-by: Nathan Sobo <nathan@zed.dev>

crates/vim/src/mode.rs

@@ -0,0 +1,36 @@
+use editor::CursorShape;
+use gpui::keymap::Context;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Mode {
+    Normal,
+    Insert,
+}
+
+impl Mode {
+    pub fn cursor_shape(&self) -> CursorShape {
+        match self {
+            Mode::Normal => CursorShape::Block,
+            Mode::Insert => CursorShape::Bar,
+        }
+    }
+
+    pub fn keymap_context_layer(&self) -> Context {
+        let mut context = Context::default();
+        context.map.insert(
+            "vim_mode".to_string(),
+            match self {
+                Self::Normal => "normal",
+                Self::Insert => "insert",
+            }
+            .to_string(),
+        );
+        context
+    }
+}
+
+impl Default for Mode {
+    fn default() -> Self {
+        Self::Normal
+    }
+}