[Request]fallback when unmatched

[uwni]

Is your feature request related to a problem? Please describe.
electron $e^-$ cannot be rendered properly currently.

Describe the solution you'd like
Fallback to math mod when no specific pattern matched

[tryptophawa]

I do think this issue has already been discussed in #35 and #33, though this issue was opened earlier. Please tell us more about the feature you wanted so we can improve it.