Why No Google Docs
Microsoft Office Extension can fix grammer issues in Google Docs but Editor can't. That is weird. Also, if you put your own word, be able to add to dictionary. Be able to ignore or put that once for a word.
Felipe Santos commented
Adding a word to dictionary is already requested here: https://office365.uservoice.com/forums/926797-office-editor-browser-extension/suggestions/40063348-allow-adding-a-word-to-dictionary