Fix focus-mode transition to small screen

[qualitymanifest]

Fix

Closes #1760

When resizing to small screen, if focus mode is enabled, keep the note open

Test

1. Open a note in full screen
2. Enable focus mode
3. Resize window small enough that isSmallScreen is true. See that note is still open, instead of switching to note-list

Review

See steps above

Release

RELEASE-NOTES.txt was updated in 9a15ac1 with:

Keep note open when transitioning to small screen in focus mode

[codebykat]

This is great, thanks so much for the fix @qualitymanifest !