Widen lxml support to include v6.x

[Mr0grog]

I don’t believe there are any changes that should be breaking for us. Changelog: https://lxml.de/6.0/changes-6.0.0.html

[Mr0grog]

I think I am going to go ahead and ship this as v0.1.7 because some downstream consumers need this compatibility, but I also plan to sprint forward on v0.2 over the next 2-3 weeks, prioritizing:

• Light cleanup on html_render_diff.py #145
• Make cChardet and html5-parser (and lxml?) optional #196
• Newer Python support (Add Python 3.11 to our testing matrix #128, Replace cChardet with something compatible with current Python versions #165, Make cChardet and html5-parser (and lxml?) optional #196)
• Add options for max diffs before restarting process #202