send correct message value for comment event, add more types of comment event

[JeffZhang02747]

This will issue #38 . Reason why commentEvent are not displayed and played sound is that, data.body is NULL, passing data.payload.comment.body instead.

handle PullRequestReviewCommentEvent and CommitCommentEvent as commentEvent.

update html accordingly.

[debugger22]

I'll test it locally and then let you know.