Respond to PR feedback

- Implemented focus_last as a python action instead of using talon script
- I was unable to test the Linux implementation and I would appreciate some help on that

core/windows_and_tabs/window_management.talon

@@ -6,6 +6,7 @@ window hide: app.window_hide()
 focus <user.running_applications>: user.switcher_focus(running_applications)
 # following only works on windows. Can't figure out how to make it work for mac. No idea what the equivalent for linux would be.
 focus$: user.switcher_menu()
+focus last: user.focus_last()
 running list: user.switcher_toggle_running()
 running close: user.switcher_hide_running()
 launch <user.launch_applications>: user.switcher_launch(launch_applications)

core/windows_and_tabs/windows_and_tabs_linux.py

@@ -38,3 +38,6 @@ def window_hide_others():
 
     def window_open():
         actions.key("ctrl-n")
+
+    def focus_last():
+        actions.key("alt-tab")

core/windows_and_tabs/windows_and_tabs_mac.py

@@ -43,3 +43,6 @@ def window_previous():
 
     def window_next():
         actions.key("cmd-`")
+
+    def focus_last():
+        actions.key("cmd-tab")

core/windows_and_tabs/windows_and_tabs_win.py

@@ -38,3 +38,6 @@ def window_hide_others():
 
     def window_open():
         actions.key("ctrl-n")
+
+    def focus_last():
+        actions.key("alt-tab")