Request: config option to set a different default case matching for regex searches

[AndydeCleyre]

Every time I use the regex search, I want to do it case-insensitively. So I type /term/i. This works, of course, but it means I don't benefit from accurate live-filtering in the view as I build the regex, as it's not "proper" until I get to the end and add the /i.

I would like to be able to set the default case-matching mode in my config. Setting it as totally case-insensitive would generally be "good enough," but even better would be something like ripgrep's -S/--smart-case matching:

Searches case insensitively if the pattern is all lowercase. Search case sensitively otherwise.

or the similar behavior seen with Zsh's extended glob flag l:

Lower case characters in the pattern match upper or lower case characters; upper case characters in the pattern still only match upper case characters.

[AndydeCleyre]

Related: #546