add active roadmap and backlog

ROADMAP.md

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+# Roadmap
+
+## Backlog
+
+- instance mapper
+- type conversions
+- dynamic binds listener
+- static binds listener
+- dynamic type visitor
+- type names by [nameof](https://github.com/Neargye/nameof)
+- non-linear search of methods/functions/...
+- register base types by `META_HPP_ENABLE_POLY_INFO`
+- distinguish between function types and function pointer types
+- add the library version to sources
+- fix all includes to work with the library more flexible
+- build and test on CI with additional flags like no-exception and no-rtti
+- `try_invoke`/`is_invocable` should return error codes
+- conan package config
+- test and support shared libraries
+- add `for_each_type` for specific kind of types
+
+## Thoughts
+
+- should `uvalue` dereference operators return `reference_wrapper`?
+- `array_view`/`pointer_view` instead `unmap`/`operator[]`/`operator*`?
+- can we add move-only uvalue analog to return move-only values?