keymap_ui: Add open keymap JSON button (#36182)

Closes #ISSUE

Release Notes:

- Keymap Editor: Added a button in the top left to allow opening the
keymap JSON file. Right clicking the button provides shortcuts to
opening the default Zed and Vim keymaps as well.
528d56e807Ben Kunkle committed on 8/14/2025, 3:29:58 PM· committed by GitHubparentf514c7c
5 files changedLine totals unavailable