`mbtn_left` and `wheel` events are now only fired on a `cursor.on_{event}` object, which resets at the beginning of each frame, so elements need to bind these listeners in their render functions. These properties are overwritable which allows elements to take over cursor event handling from their parents if necessary.
* fix: only update resolution when it's > 0
* fix: only render after the resolution has been initialized
* chore: update type annotation to fix warning
- Preselecting previous folder wasn't working sometimes.
- `join_path()` didn't account for drive letters already having a separator.
Also refactors how `open_file_navigation_menu()` stores menu items value. As a side effect this is now a lot faster as we don't have to serialize each item's path into meta table, but instead we now store just a path string and handle it as needed.
closes#355
Instead of calling `utils.readdir()` twice to get directories and files, we now read the directory only once and sort it by item type. Also optimizes extension checking.
ref #344
