ILS is a browser extension that colorizes issue and PR links to see their status (open, closed, merged). It uses GraphQL to make a single HTTP request to check all the links on a page at once. This means that you'll need to create a API token and add it to the Options page or else the extension will not work.
GitHub Enterprise is also supported. More info in the options.
The chrome version also works in Opera (using this) and Edge.
- Refined GitHub - Browser extension that simplifies the GitHub interface and adds useful features