Shorten automatic description of attachments, comments and milestones

[btlogy]

Similarly to #19, a link to a comment is also described with a rather long text which could be shorten.

For instance: [/user_name/repository_name/issues1#issuecomment-1234](/user_name/repository_name/issues1#issuecomment-1234)

Would look better as: [user_name/repository_name#1:1234](/user_name/repository_name/issues1#issuecomment-1234)

Or even better in case the comment is in the same issue: [#1:1234](/user_name/repository_name/issues1#issuecomment-1234)

Though, it might be way simpler to just do the following (assuming the comment id id unique enough): [issuecomment-1234](/user_name/repository_name/issues1#issuecomment-1234)

Same goes for milestones and attachment for which we should stick to the original lint text as much as possible.

E.g.:

• milestone:my-next-feature
• attachment:my-simple-file.txt