Add XML inhibit tags

[LiterallyVoid]

This adds an option to disable typo-mode inside specified XML tags, for example <code> and <pre> if you're going to be writing HTML.

Concerns:

• Should this be enabled by default, and which tags should be in typo-xml-inhibited-tags? Currently, it's not enabled by default, and some HTML tags (<pre>, <code>, <kbd>, and <samp>) are in the default typo-xml-inhibited-tags list.
• I haven't tested performance, but it should be roughly the same as checking if it's inside an XML tag, i.e. the per-keystroke cost would be doubled, if enabled.
• The names I've chosen for these customization options feel a little awkward (typo-inside-xml-inhibited for the query function; typo-xml-inhibited-tags for the list of tags to check for.)