Bug 987496 - Adding Hindi Input Method for B2G

Cherry-pick from 7882bd086a460ff07b170ed45a1cf8981f4d0f72

Conflicts:

  build/config/keyboard-layouts.json
Merge pull request #23121 from luke-chang/987496_v1.4_hindi_input_method

Bug 987496 - Adding Hindi Input Method for B2G