Document new desired feature

CHANGELOG.md

@@ -6,6 +6,7 @@ Changelog
 - Added support for quickly exposing functions as cli clients with `hug.cli` decorator
 - Added support for quickly serving up development APIs from withing the module using: `if __name__ == '__main__': __hug__.serve()
 - Added support for documentation only type annotations, simply by passing just a string in as the type annotation
+- Added support for `only_if` argument to limit exposure of functions based on a given criteria
 - Added automatic documentation of output type transformations
 - `hug.types.decimal` renamed to `hug.types.float_number` and `hug.types.decimal` type added that returns python Decimal
 - `hug.types.accept` wrapper added, that makes it easy to customize doc strings and error handling for any preexisting type converter