Discoverability of CIP-30 extensions

[Ryun1]

• CIP-30 has some extensions, but from reading CIP-30 that is not obvious.
• We have had several extensions to CIP-30 lets list them in a central place so implementors can discover.
• maybe also update https://www.cardano-caniuse.io/

[Ryun1]

Probably easiest to add a extension register to CIP-30

[Crypto2099]

Would the register be managed/maintained by the editors? Probably easiest to do it this way to ensure it is done consistently versus expecting authors of new extensions which may introduce merge-conflicts?

[Ryun1]

Something like this?

Fixed by #980.