feat: add customisable spellcheck

[DeepanshKhurana]

Related Issue:
Fixes #4

Description of Changes:

• Spell check now supports 80+ languages powered by hunspell, including Hungarian, Arabic, Polish, French, and many more. Language is set per profile during setup and can be changed any time in manage profiles.
• Spell check language selection is part of the setup wizard and the new profile flow.
• Existing users are prompted to set a language on first launch after upgrading, with the option to configure each profile individually.
• --languages flag lists all supported language codes with names.
• Spellcheck settings persist per profile.
• Spell check on/off toggle added to edit and new profile modals (ctrl+k).
• SPELL CHECK section added to --reference.

Additional Notes: