Add TODO with known issues

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: trans

TODO.md

@@ -0,0 +1,16 @@
+# TODO
+
+## Known Issues
+
+- **Global `$skip` variable** (overload.rb) — Used to prevent recursive
+  `method_added` triggers during overload setup. Works but is fragile.
+  Fixing properly would require rethinking the `method_added` hook.
+
+- **No keyword argument support in overload dispatch** (overload.rb:57) —
+  The dispatch method uses `|*args|` which swallows kwargs on Ruby 3.
+  Since Platypus dispatches on positional argument types, kwargs aren't
+  part of the current design. Adding support would be a feature addition.
+
+- **`Type::Conditions` uses old blank slate pattern** (type.rb:88) —
+  Privatizes all methods except `__` prefixed ones. Works on Ruby 3
+  but could be modernized to use `BasicObject`.