One of the things that's done when the site is generated for GitHub Pages and when a new pull request is submitted is every .md file is checked for spelling errors using this workflow.
When submitting a pull request, all checks should pass before the pull request can be accepted. So, when the spellchecker finds a word that it mistakenly finds to be misspelled, then the word should be added to a list of words to be ignored by the spellchecker. The word list is located in the repository root, saved as .wordlist.txt. Once the word is added and the pull request is updated, then all checks should pass and the pull request can be approved.