Improve errors

[peter-bread]

• If an empty local config is found, the error message is Error: EOF which isn't exactly helpful.

Could be worth actually learning best practices for more useful errors.

[peter-bread]

gamon3/internal/config/local_config.go

Lines 46 to 50 in 697e0bc

	decoder := yaml.NewDecoder(bytes.NewReader(data), yaml.DisallowUnknownField())
	var cfg LocalConfig
	if err := decoder.Decode(&cfg); err != nil {
	return nil, fmt.Errorf("%s", yaml.FormatError(err, true, true))
	}