Load discovers and loads config. It returns the loaded config along with
the path that was loaded — either the matched repo config filename in the
current directory (".bight.yml" or ".bight.yaml") or, if only the global
config exists, the global config path.
LoadFrom loads config from a specific repo config file path, merging with
the global config (~/.bight.yml) as usual. Unlike Load, it does not search
for .bight.yml or .bight.yaml in the current directory. The returned path
is the repo config path that was loaded.