local links in `README.md` are not resolved correctly

[0xdea]

Just a minor hiccup I noticed. When generating a plugin repository page based on its README.md on GitHub, local markdown links are not resolved correctly. For instance, in this README.md document we have the following entry:

## Changelog

* [CHANGELOG.md](CHANGELOG.md)

In the corresponding plugin repository, the link is resolved as https://plugins.hex-rays.com/0xdea/CHANGELOG.md, which of course is broken. It should instead be resolved as https://github.com/0xdea/rhabdomancer/blob/master/CHANGELOG.md.

[williballenthin]

thanks for pointing this out. it will probably take some iteration to get right, since i expect most people develop their readme for github and then it happens to mostly work for plugins.hex-rays.com.