Transpilation of .ignoreCase for HTML `pattern`

[tigt]

No, really. I’m sure that sounds bizarre but I have a reason.

On my Node server, I'm generating HTML that uses the pattern attribute. Ideally, it would look something like this:

<input pattern="<% /^foo.bar$/i.toSource %>">

However, the pattern attribute is specified to act like it only has the u flag. regexpu helps me with my server-side regexes that use dotAll and such for older browsers, but i can’t be used.

Would it be in-scope to add ignoreCase as an option for regexpu?