Read default values of all flags from ~/.goreturns.json file

[ilius]

Since vscode does not accept custom command / flags for goreturns, this seems the best way to add flags (for example -local in our case). Create a ~/.goreturns.json file with this template:

{
	"fragment": false,
	"printErrors": false,
	"allErrors": false,
	"removeBareReturns": false,
	"local": ""
}

Passing flags will override these values.