* Make prototype with enterpolation before parsing
* Add test for option.from_yaml() with missing env not required
* Make some cosmetic changes to _resolve_config_env_markers()
* Add test for option.from_ini() missing envs not required
* Skip schema test cause it requires internet connection
* Add tests for .from_yaml() for config and config option
* Add tests for .from_ini() for config and config option
* Add example for os.environ.setdefault() and envs interpolation
* Add/update docs on environment variables interpolation
* Update changelog
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