Add special badge at the start of the changelog item.

[andy840119]

Should be able to change the prefix into the badge.
Also, should change the prefix word into the key, e.g.

• [Close duplicated] -> [duplicated]
• add new [outdated] prefix.

[andy840119]

Note:

1. maybe just outdated badge is enough.
2. maybe changed the format to <badge>outdated</badge> or [outdated] will be easier to handle while rendering?

[andy840119]

Implemented