feat: add fromJSON support (#352)

pkg/runner/expression_test.go

@@ -80,6 +80,8 @@ func TestEvaluate(t *testing.T) {
 		{"join('hello','mona')", "hello mona", ""},
 		{"toJSON({'foo':'bar'})", "{\n  \"foo\": \"bar\"\n}", ""},
 		{"toJson({'foo':'bar'})", "{\n  \"foo\": \"bar\"\n}", ""},
+		{"(fromJSON('{\"foo\":\"bar\"}')).foo", "bar", ""},
+		{"(fromJson('{\"foo\":\"bar\"}')).foo", "bar", ""},
 		{"hashFiles('**/package-lock.json')", "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", ""},
 		{"success()", "true", ""},
 		{"failure()", "false", ""},