Bug

The HTML_LOWER_CASE regex used to determine which attributes should be lowercased
can falsely match custom element properties. For example, passing channelId to a
custom element results in channelid because the regex matches the ch prefix
(intended for charSet).

Reproduction

// Code
<my-fragment channelId="abc123" />
// Expected
<my-fragment channelId="abc123" />
// Actual
<my-fragment channelid="abc123" />

Cause

The regex ^(?:accessK|auto[A-Z]|cell|ch|col|...) uses broad prefixes that can
match unrelated property names on custom elements.

Proposed fix

Replace the regex with an explicit Set of known camelCase HTML attribute names
and use .has() instead of .test().