feat!: Require type to be specified for each supplied option

[shadowspawn]

Currently the type property is optional and defaults to boolean, but this is a bit opaque.

Closes: #94

Make it an error to leave out the type:

parseArgs({
  options: {
    foo: { },
  },
});

ERR_INVALID_ARG_TYPE [TypeError]: options.foo.type must be ('string|boolean') got undefined

Correct:

parseArgs({
  options: {
    foo: { type: 'boolean' },
  },
});