core: add "reset" keybinding to reset the terminal

Fixes #1425

src/Surface.zig

@@ -2920,6 +2920,12 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !bool
             try self.io_thread.wakeup.notify();
         },
 
+        .reset => {
+            self.renderer_state.mutex.lock();
+            defer self.renderer_state.mutex.unlock();
+            self.renderer_state.terminal.fullReset(self.alloc);
+        },
+
         .copy_to_clipboard => {
             // We can read from the renderer state without holding
             // the lock because only we will write to this field.

src/input/Binding.zig

@@ -143,6 +143,15 @@ pub const Action = union(enum) {
     /// (`application`) or disabled (`normal`).
     cursor_key: CursorKey,
 
+    /// Reset the terminal. This can fix a lot of issues when a running
+    /// program puts the terminal into a broken state. This is equivalent to
+    /// when you type "reset" and press enter.
+    ///
+    /// If you do this while in a TUI program such as vim, this may break
+    /// the program. If you do this while in a shell, you may have to press
+    /// enter after to get a new prompt.
+    reset: void,
+
     /// Copy and paste.
     copy_to_clipboard: void,
     paste_from_clipboard: void,