Add some tests and move some docs

FU.pm

@@ -2,3 +2,19 @@ package FU 0.1;
 use v5.36;
 
 1;
+
+__END__
+
+=head1 NAME
+
+FU - A collection of awesome modules plus a lean and efficient web framework.
+
+=head1 SYNOPSIS
+
+=head1 DESCRIPTION
+
+=head2 Properties
+
+- Requires a moderately recent Perl (>= 5.36).
+- Only works on 64-bit Linux (and possibly *BSD).
+- Assumes that no threading is used; not all modules are thread-safe.