HTML Attribute values converting to lowercase

[panoply]

Description

This issue is something that I believe to had introduced in the lexer during refactors. Could be something I considered a good idea during lack of sleep. Whatever the case it is problematic. Take the following:

<div id="Foo" data-attr-something="SoMeThInG"></div>

The above code will be converted to:

<div id="foo" data-attr-something="something"></div>

While this is fine for a lot of situation it is not nice for situations where one is using a framework like Stimulus, Alpine or a use case which requires case preservation.

Ruleset

I believe this calls for a new ruleset to be introduced. In some situation folks might want to enforce lowercase while others might want to preserve the case structures, it will vary. By default, casing should be preserved as it was provided and users should optionally enable enforced lowercase. I will create a separate issue going into more detail regarding this.