🐛 [#607] Patch regex for phone number validation

The first character of the phone number may only be a plus sign or
a number (4-digit phone numbers can be called, so only allowing a
zero would be too strict). For grouping, dashes and spaces may be
used, but these characters are not valid for the first character.

src/formio/components/PhoneNumberField.js

@@ -4,7 +4,7 @@ import enableValidationPlugins from '../validators/plugins';
 
 const PhoneNumber = Formio.Components.components.phoneNumber;
 
-const PHONE_NUMBER_REGEX = /^\+{0,1}[- 0-9]{0,}$/;
+const PHONE_NUMBER_REGEX = /^[+0-9][- 0-9]+$/;
 
 const PhoneNumberValidator = {
   key: 'validate.phoneNumber',