To save on some of that manual activity, I created a new userscript today: Github: Twitter Link.
You can check it out here:
Here is the current description from README.md:
This is a user script that adds a twitter link on Github profile pages if a corresponding user name exists at Twitter. It utilizes local storage to minimize multiple Twitter API requests. If a corresponding user name is not found, then we will not check for it again. At some point I may add a "time limit" on when to check again.
Before installing the user script:
After installing the user script:
Twitter account exists:
Twitter account doesn't exist: