Get this extension
Google Chrome
https://chrome.google.com/webstore/detail/gameminernet-autojoin-bot/ehnlgmgdeiniedehbamagbfbljmhekdm
Opera
https://addons.opera.com/en/extensions/details/gameminernet-autojoin-bot/
Mozilla Firefox
Mozilla is currently working on a new extension format. As soon as it is ready (currently only available in nightly version) This extension will be published for Firefox too. Until then, sorry that it is not available for your favorite browser.
If you have any suggestions contact me on Steam.