Support ".hocon" extension about config

[havocp]

The rationale is that the file may not be a config file?

[foror]

I think it requires a more global refactoring... And a new library, that only work with HOCON format (like json libraries). But while I thought to make a small patch to support HOCON, without a lot of refactoring and create a new library.

[foror]

Or someone might want to give the name of the configuration file as "config.hocon" :)

[farquet]

Projects like GraalVM use the .hocon extension. I think it would make sense to make it a first class citizen in the official hocon implementation since it's a very unambiguous extension name.