Live docs pages feature a Edit on GitHub link in the footer. Clicking this link will automatically take you to that page’s associated .md file in the repo.
From there you, make sure you’re signed into GitHub. Once signed in, you’ll be able to click the pencil icon in the top right corner of the file to start editing the document right from within the browser.
GitHub will then guide you through making a commit and ultimately a pull request with your proposed change.