Add Cheonjiin keyboard with flick support

[kompackvenom]

Summary

This PR adds the Korean Cheonjiin keyboard with flick support.

Features

• Add Cheonjiin keyboard layout
• Support directional flick input
• Display flick popup labels
• Support Hangul vowel composition
• Support symbol/number keyboard switching
• Preserve existing tap input behavior

Tested

• Tap input
• Flick input
• Compound vowels
• Backspace
• Symbol/number keyboard switching

[Lee0701]

Updated layout for new code.

[kompackvenom]

It needs to be modified such that area ㆍ and double area ᆢ can be typed. This is not only needed in the feature of potential old hangul expansion but also in modern cheonjiin keyboard.

[Lee0701]

• Added dot and double dot to visible vowels list (uses Katakana middle dot and fullwidth colon respectively for display)
• Use space instead of dpad right for confirm input key (Most of implementations use this method)