Finish loading the vscode examples v1; Improve on the infra: Add accessibility tree into the observation; Add activate window function, etc

desktop_env/envs/desktop_env.py

@@ -221,6 +221,7 @@ class DesktopEnv(gym.Env):
         time.sleep(pause)
         observation = {
             "screenshot": self._get_obs(),
+            "accessibility_tree": self.controller.get_accessibility_tree(),
             "terminal": self.controller.get_terminal_output(),
             "instruction": self.instruction
         }