As my answer with CoLT is only valid for Firefox < v57 (and CoLT won't be maintained anymore), a good replacement is Format Link: excellent support by the dev.
Again, no Ctrl-C directly on the page, but a context menu is available. There's also a toolbar button available which lets you edit the captured text, and switch between the formattings. Next to some preconfigured formats, you also can define your own.
Format Link: toolbar button (opened), context menu entry (click images for larger variants)
For the context menu you can either have your preferred format as single entry, or a sub menu with all configured formats. Unfortunately, not both at the same time – again a limitation of Mozilla's WebExt API.
A Plus of this addon is: If you mark some text anywhere on the page, and then use the context menu to capture the URL (either of a link on the page when right-clicked on it, or of the entire page when right-clicked in an empty area), the marked text will be taken as description for the link.
Note however that none of the new WebExt stuff can work on Mozilla's own pages. That's not the fault of the AddOn devs, but of Mozilla locking that (in the API and on their site). Remember that compared with the previous API, WebExt is very limited – and many AddOns lost functionality.