feat: Add P.nonNullable patterns

[gvergnaud]

P.nonNullable wildcard

Add a new P.nonNullable pattern that will match any value except null or undefined.

import { match, P } from 'ts-pattern';

const input = null;

const output = match<number | null | undefined>(input)
  .with(P.nonNullable, () => 'it is a number!')
  .otherwise(() => 'it is either null or undefined!');

console.log(output);
// => 'it is either null or undefined!'

Closes #60 #154 #190 and will be a work-around for #143.