Just like #43747 added the keybinding(s) for `settings.json`, added them
here for keymaps and added the tooltip to show those.

<img width="500" height="282" alt="Screenshot 2026-01-04 at 2  47@2x"
src="https://github.com/user-attachments/assets/d4dbdd6e-24eb-4b7f-baa8-6e1d9810ff94"
/>

Release Notes:

- keymap editor: Added the ability to open the `keymap.json` file with a
keybinding.

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Co-authored-by: Danilo Leal <daniloleal09@gmail.com>