rpm-4.20 announce should speak about API changes

[soig]

https://rpm.org/wiki/Releases/4.20.0 doesn't list any API changes. But :

• the internal OpenPGP parser has been removed so rpm/rpmpgp.h saw a lot of changes
• there's a new rpmdsIsSysuser() function
• there's a new rpmMacroBuf class with the associated API
• …

This should be listed.

[dmnks]

Good point, the API section has been forgotten. Thanks, we'll add it.

[dmnks]

Moved to the rpm repo to make it easier to track: https://github.com/rpm-software-management/rpm/issues/3273