Add-On: Let's Encrypt with ECDSA

I wanted to start using ECDSA keys with the Let’s Encrypt add-on, a journey which ended up at making my own version of the add-on with new options for EDCSA.

I tried to get a PR merged but there was disagreement about options: I think users should have the option to choose between RSA and ECDSA keys, the official add-on does not. So I made my own version that adds options for ECDSA or RSA, and two curve options for ECDSA.

Note: RSA is still the most backwards compatible with older devices or operating systems that won’t be updated to support ECDSA, but anything in the last 5+ years should support ECDSA.

Depreciated - features now available in official add-on starting with version 5.0.13