convert CamelCase tags to kebab-case

[jackhogan]

handle CamelCase tag imports from fasthtml.components similarly to from fastcore.xml

[jph00]

Maybe consider a followup PR which refactors the dupe code into fastcore so we don't end up with a similar issue next time we make a change like this? (This is my bad in the first place for reimplementing this!)

[jackhogan]

Thanks @jph00, I refactored the duplicated code in fastcore so the implementation can be shared. See

• extract tag conversion logic to unify __getattr__ with fasthtml fastcore#838
• use mk_getattr from fastcore to unify __getattr__ implementation #899