Inaccurate path of config.json overriding the default config in README

[hungrydonkey]

In Global Configuration of README, it says that for most cases it just means $*HOME/.zef/config.json will override an installed zef configuration file. But actually the path should be $*HOME/.config/zef/config.json

[ugexe]

Looks like that was broken in https://github.com/ugexe/zef/commit/c5635d74fe18538770842517c024577f20310929#diff-0b87bf9585ac7013f75b9ed789159ff7023c204e52596ff6670d06bbda3d9787

[hungrydonkey]

Looks like that was broken in c5635d7#diff-0b87bf9585ac7013f75b9ed789159ff7023c204e52596ff6670d06bbda3d9787

Yeah, now $*HOME/.zef/config.json is not working, since in https://github.com/ugexe/zef/blob/7d6b48db23eaca06c332fa6d0ca8ecae80ae83d4/lib/Zef/Config.rakumod#L21, the @path-candidates doesn't contain that path. I think README should be changed correspondingly.