[Feature] Implement .gitbugtraq

[SoulSeekkor]

It would be great to implement this spec into Gitea:
https://github.com/mstrap/bugtraq

For work and home I use SmartGit, and the software recognizes .gitbugtraq files at the root of the repo making it ideal to hyperlink to multiple issue trackers (or anything else really) using regex.

This is an example of one I use for work that links to both Autotask tickets as well as JIRA issues.

[bugtraq "jira"]
 url = http://x.x.x.x/browse/%BUGID%
 logRegex = "(?:^|\\s|"")([A-Z]+-\\d+)(?:\\s|:\\s|/)"
[bugtraq "autotask"]
 url = https://xxx.autotask.net/Autotask/AutotaskExtend/ExecuteCommand.aspx?Code=OpenTicketDetail&TicketNumber=%BUGID%
 logRegex = T\\d{8}.\\d{4}