Download at Chrome Webstore https://chrome.google.com/webstore/detail/easy-github-repo-delete/adoiopbekmljhndnefhmagpfgioedfae
Deleting repos on github can a little long process(and for the right reasons because its an irreversible action) and when you have a lot of github repos to delete it can be very time consuming.
Click the extension icon on top-right to get started. Lists all your repo with delete button when provided with Github personal access token, you can get one at https://github.com/settings/tokens
After clicking delete that repo will get deleted without any warning, so better be careful.