Bug 1049279 - [Keyboard][ja] Recover Japanese ime dictionary for jp-kanji

Update README and Makefile to apply naist-jdic

fix the raw dict file (dict.utf8) with conv.py instead of a diff patch
Merge pull request #22601 from marsf/keyboard/Bug1049279

Bug 1049279 - [Keyboard][ja] Recover Japanese ime dictionary for jp-kanji