Fallback to filesystem and mouse events to track any app

[alanhamlett]

To start sending heartbeats for apps that don't support Accessibility events, we'll start watching keypress and filesystem events. The combination of keypress and filesystem events will be called Fallback events (our own term).

Using Fallback events, we can start tracking any mac app not just known ones. To do that, we need:

• Detect all installed apps from /Applications/ and list those apps with their icon and name in the Monitored Apps settings menu so they can be enabled for tracking. Only known apps (Xcode, Figma, Postman) will be enabled for tracking by default.
• Xcode will use Accessibility APIs while all other apps will start by using Fallback events and switch to Accessibility events if we see them triggered for that app. When we get an Accessibility event for an app, turn off tracking Fallback events for that app until WakaTime.app is re-launched.
• When using Fallback events for an app, keep track of the last edited file for that app and use keypress events to trigger sending heartbeats for that file. Only keep track of files which we've detected a WakaTime project, to avoid tracking system and temp files that the app might have open.

[alanhamlett]

Update: With #109 we ran into a problem with too many filesystem events unrelated to the currently focused app. Not sure how to filter down to only those fsevents for a specific app, so we might have to postpone this work.

[alanhamlett]

Update: We're tracking Figma and Postman now as entity type app using the window title as entity.

We should still look into detecting a focused file, then use the window title as the project.

[alanhamlett]

Implemented with #218 where we track the last time a key was pressed or the mouse moved, and then look through the a11y dom to find entity and sometimes project.