Due to scenarios wherein a formatted link ended up as part of a larger
raw link after parsing, change the containment check to an overlap check
and add appropriate tests for these edge cases.
Testing with #6542 surfaced a crash scenario, caused by formatted links
that had URLs in the display text, for example
[mean example - https://osu.ppy.sh](https://osu.ppy.sh)
In that case the outer Markdown link would get picked up once, and then
reduced to the link text when looking for other links, leading to it
being picked up again the second time when the raw link is found.
Add a check in the raw link parsing path that ensures that the found
URL is not a part of a bigger, pre-existing link.
While reviewing #6542 it became apparent that there was another Markdown
link format variant, used in comments that came from the web API, called
the "inline link" style. It allows to specify the tooltip title within
the actual URL portion, as such:
[link text](https://osu.ppy.sh "tooltip text")
Add tests with a couple of easy and trickier examples of such a format.
Moreover, add a new edge case of a Markdown link with a link inside
the display text, which during tests was detected to be problematic.
Add a test case reproducing the conditions encountered "in the wild"
wherein a skin import would be performed incorrectly due to a __MACOSX
resource fork directory present next to a directory with the actual skin
files in the archive.
