Allow empty fragments in HTML parser (astral-sh#1443)

## Summary

It looks like `devpi` might add an empty fragment (`#`) at the end of
the URL. We expect it to contain the hash; this just makes
empty-fragment map to "no hash".

Closes astral-sh#1441.

Bump version to 0.1.1 (astral-sh#1359)

Bump version to v0.1.0 (astral-sh#1325)

Rename `PUFFIN` environment variables to `UV` (astral-sh#1319)

A couple of these are actually user-facing although undocumented