Extension completions

[itepastra]

Add completions for the various htmx extensions.
for #14

thanks to @WillLillis for making a framework to add the extensions

TODO:

• add actual documentation for the attributes
• add actual documentation for the tags
• make additional tags for existing attributes work (for example: idiomorph adds hx-swap="morph")
• make tags that don't start with hx- work in the tests (some seem to work correctly in actual files)
• the classes attribute from class-tools is not completed