Disable spellcheck in certain cases automatically

[xsrvmy]

Description

There are a few contexts were spellcheck does not make sense and it would be nice to disable them.

1. All caps (this could be an option)
2. Anything that precedes or follows math without a space (this mirrors any word containing numbers not being spellchecked)

Use Case

$i$th should not be flagged, but missing the "e" the end of "the" should be.