The behavior that you have described is already present in Firefox. Holding Ctrl and clicking on a link will open the link in a new tab. There are some cases in which a website can override this, but it works on most websites.

If it's not working for you, try running Firefox in Safe Mode to ensure that it's not an issue with something that you may have installed on Firefox.

Use this link to test.

Note that you can also middle-click a link with the mouse scroll wheel. This might not work properly if there is a JavaScript onclick handler used.