Doesn't Handle String Union Types with Quotes inside Backticks

[dsanders11]

This is definitely a corner case, but currently prevents this example in the docs from being typed properly: https://github.com/electron/electron/blob/ce4ae584e357000b324228693ed7556922b6335f/docs/api/client-request.md?plain=1#L54-L58

I tried single quotes rather than double quotes with the same result, so the issue is quotes inside of the backticks. This might be tricky to make parse correctly with the current regex approach.