Correction not using bi-grams

[ierezell]

I raised an issue on the original symspell wolfgarbe/SymSpell#110 but maybe it can come from the port too.

In a nutshell, it's the correction using unigrams only.
For example perce wue being corrected as perce que with perce in the unigrams que in the unigram but perce que not in the bigrams dictionary (and it don't mean anything, it should be parce que).

Do you have any idea of where it can come from?

I can help and do a PR, just point me to the right place :)

Have a great day