Flag mixing up "were" and "where"

**The Error**
It's quite common to accidentally type "where" when you mean to type "were". I know I've caught myself doing it. I was just reminded of this when I came across it online now.

The opposite may also happen but probably to a lesser degree.

(Unfortunately I lost my example I was going to include due to the GFW throttling everything while trying to start posting this issue.)

No file, test, or implementation entry point is named. Start by locating the existing grammar rules for “were” and “where,” then determine how comparable confusion rules are tested; done means the checker flags both mix-ups without incorrectly flagging valid usage.

Written by the indexing model from the issue text.