I frequently use JsonNode as a container for Any object. Another use case is how it's used for JSON, YAML, XML, etc. formats. Right now every such library had to create its own object mapper. While it would be much easier if `std/any` provided the `Any <-> Nim` conversions, and the custom library only need to provide `Any <-> JSON/YAML/XML`.
It will also make possible to easily switch between formats. You set some custom serialisations for your objects to JSON. And now you want to also save it to YAML, but you can't because YAML is totally different library and you need to specify custom serialisation rules again. But with `Any` it would work well, as it's going to work like this `Nim <- custom rules -> Any` and then totally independent `Any <-> JSON/YAML/...` What do you think?
