Finding code & documentation for this extension took more steps than it should have, particularly due to the extension being called 'Alice - Spell Checking' in the extension manager but 'Linguistics' on its home page.
Note that this issue is against the latest extension manager version (see 3b0a4b9022) Those commits haven't been pushed here yet (please do so, @JohnathonKoster).
In the extension manager the homepage is currently set to https://stillat.com. It would be much more helpful to set https://github.com/JohnathonKoster/brackets-spellcheck. Pointing to github is typical, but I guess https://stillat.com/blog/2017/10/31/installing-linguistics-for-adobe-brackets would also be acceptable if you want to reference stillat.
Finding code & documentation for this extension took more steps than it should have, particularly due to the extension being called 'Alice - Spell Checking' in the extension manager but 'Linguistics' on its home page.