Document .WRITE/.READ/.EOF on IO::CatHandle

These just throw X::NYI; blocking out these methods from IO::Handle

SAP (Spec APpendices): Raku/roast@e0f6f389d5
Rakudo impl: rakudo/rakudo@9246b03520

doc/Type/IO/CatHandle.pod6

@@ -832,6 +832,36 @@ In Rakudo, the L<IO::CatHandle> type overrides this method to throw C<X::NYI>
 exception. If you have a good idea for how this method should behave,
 L<tell Rakudo developers about it|https://webchat.freenode.net/?channels=#perl6-dev>!
 
+=head2 method WRITE
+
+Defined as:
+
+    multi method WRITE(|)
+
+In Rakudo, the L<IO::CatHandle> type overrides this method to throw C<X::NYI>
+exception. If you have a good idea for how this method should behave,
+L<tell Rakudo developers about it|https://webchat.freenode.net/?channels=#perl6-dev>!
+
+=head2 method READ
+
+Defined as:
+
+    multi method EOF(|)
+
+In Rakudo, the L<IO::CatHandle> type overrides this method to throw C<X::NYI>
+exception. If you have a good idea for how this method should behave,
+L<tell Rakudo developers about it|https://webchat.freenode.net/?channels=#perl6-dev>!
+
+=head2 method EOF
+
+Defined as:
+
+    multi method EOF(|)
+
+In Rakudo, the L<IO::CatHandle> type overrides this method to throw C<X::NYI>
+exception. If you have a good idea for how this method should behave,
+L<tell Rakudo developers about it|https://webchat.freenode.net/?channels=#perl6-dev>!
+
 =end pod
 
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