optional path params

[dbushong]

one might wish to write a client like this:

class Foo extends Gofer {
  constructor(cfg) {
    super(cfg, 'foo');
  }

  bar({ x, y }) {
    return this.get('/{x}/{y}', {
      endpointName: 'bar',
      pathParams: { x, y },
    });
  }
}

const foo = new Foo({ foo: { pathParams: { x: 'whee' } } });
await foo.bar({ y: 'yay' });

with the current types, it will complain that you're passing an
undefined value as a pathParam, but really that will be dealt with in
the config merging later on, so we should accept it

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This PR was started by: git wf pr

[aotarola]

💚