Make parse/format required if custom pattern is used.

[MrMarble]

Hi, just wanted to contribute to your amazing repo! This change fixes #973

If the user provides the default pattern, the type check is ignored

Here's a screenshot of vscode showing the different cases, default pattern, custom pattern with error, custom parse without error and custom pattern with format and parse without error

[uNmAnNeR]

@MrMarble thank you!