Clarify maintenance mode

Looking through recent issues, this seems to be roughly the current situation. Making it clearer here, to help users evaluating this lightweight library against the heavier-weight pgx. But I confess, I might be guessing totally wrong.

Whether or not this PR content is right, I just want to say thanks to the maintainers of this library. We're using it at Camus Energy to help grid operators decarbonize, a.k.a. fighting climate change. We're really happy this library exists, because it serves our needs better than pgx. Really, thanks 😃

README.md

@@ -27,4 +27,10 @@
 
 ## Status
 
-This package is effectively in maintenance mode and is not actively developed. Small patches and features are only rarely reviewed and merged. We recommend using [pgx](https://github.com/jackc/pgx) which is actively maintained.
+This package is currently in maintenance mode, which means:
+1.   It generally does not accept new features.
+2.   It does accept bug fixes and version compatability changes provided by the community.
+3.   Maintainers usually do not resolve reported issues.
+4.   Community members are encouraged to help each other with reported issues.
+
+For users that require new features or reliable resolution of reported bugs, we recommend using [pgx](https://github.com/jackc/pgx) which is under active development.