Config: Support env XRAY_JSON_STRICT=true (#6053)

https://github.com/XTLS/Xray-core/pull/6053#issuecomment-4363840170

---------

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

main/json/json.go

@@ -41,6 +41,13 @@ func init() {
 				}
 				return cf.Build()
 			case io.Reader:
+				if serial.UseStrictJSON {
+					cfg, err := serial.DecodeJSONConfigStrict(v)
+					if err != nil {
+						return nil, err
+					}
+					return cfg.Build()
+				}
 				return serial.LoadJSONConfig(v)
 			default:
 				return nil, errors.New("unknown type")