fix: Remove all punctuation from anchors in policies.md

[zephyrdb]

Punctuation breaks anchor links in Markdown. This implements the same rule as GitHub.

(While testing, I realized that it's probably also important to escape Markdown characters in other fields. I didn't do that for the description, in case someone actually wants to use Markdown there.)

[jalseth]

Thanks for the PR!

[zephyrdb]

So uh, I added a test in the form of an example. Which isn't ideal, but it's the only way to be sure that not only does the code work, the Markdown does what it says on the tin. I found a number of odd things in the course of that, including the part where cmd-click in VSCode works on the anchor in the editor (once I removed trailing space), but clicking in my Markdown preview plugin doesn't. It seems to be ok on GitHub, though, and it's a pretty contrived example to begin with. I'll do a little more poking around tomorrow just in case.

[zephyrdb]

Ok a bunch more work later, I think this is as thorough as it can possibly be without being unreasonably complicated and resource-consuming.

[jalseth]

Thanks!