Keyboard shortcuts are displayed as "Ctrl" in browser, including on the Mac

We could test this in a more sophisticated way

https://github.com/Automattic/simplenote-electron/blob/develop/lib/dialogs/keybindings/index.tsx#L43

and

https://github.com/Automattic/simplenote-electron/blob/develop/lib/utils/platform.ts#L4

### Expected
Keybindings should display with Cmd on Mac browsers

### Observed
Keybindings are displayed as Ctrl unless using Mac on Electron

Start by reading lib/dialogs/keybindings/index.tsx around line 43 and lib/utils/platform.ts around line 4 to trace how browser and Electron platforms choose shortcut labels. Verify the behavior in a Mac browser and compare it with Electron; done means keybindings display Cmd on Mac browsers while retaining the observed behavior elsewhere.

Written by the indexing model from the issue text.