Add Cangjie 3 code "raiu" for character "嘅"
The character "嘅" has a different glyph in different Chinese
standard. The mapping to 口日戈山
("raiu") makes better sense
for the Hong Kong glyph standard.
The mapping exists in Cangjie 5 already. It is now added to Cangjie 3 also.
Fixes #93 (closed).