feat(TCMention): rewrite mention detection using different algorithm
feat(TCMention): rewrite mention detection using different algorithm

BREAKING CHANGE: detect the "word" based on current caret position

    The intention is to make its behaviour much closer to Facebook/Medium. Also rename the option of `autoHideOnBlurDelay` to `hideOnBlurDelay`.

    Before:

    The user type in @ or # to trigger mention panel immediately. If you already type one and navigate it back to the position using your arrow keys on keyboard, the mention panel won't show up this time.

    After:

    The user has to type in @ or # with one more word to trigger mention panel. Navigating back to the word will show up the mention panel.

tomchentw/medium-editor-tc-mention