Docs, compatibility fixes again, 0.1 release

FU.pm

@@ -819,6 +819,14 @@ __END__
 
 FU - Framework Ultimatum: A Lean and Efficient Zero-Dependency Web Framework.
 
+=head1 EXPERIMENTAL
+
+This module is still in development: it's missing important functionality and
+there will likely be a few breaking API changes. This framework currently
+powers manned.org as a test. I'll do a stable 1.0 release once FU is used in
+production for vndb.org, which will take a few months in the best case
+scenario.
+
 =head1 SYNOPSIS
 
   use v5.36;