Why would I do that? In case of an extension is not available on stores, you can install it by yourself. The original repository will probably exists and continue to serve releases.
➡ Go to Github Releases page to download the latest ZIP source files and follow these steps regarding your browser.
- Unzip the downloaded source files
- Open the Extensions page (chrome://extensions/) in the browser
- Turn on the "Developer mode" (top-right of the page)
- Click on the "Load unpacked" button and select the directory where the built extension is placed
- Rename the .zip downloaded file to .xpi
- Open the Add-ons page (about:addons) in the browser
- Click on the gear icon (on top-right), and click on "Install Add-on from file"
- Open the .xpi file from the extracted folder