Allow iPhone to be classed as a 'phone'

[kgodsmark]

Some iPhone user agent strings are not matching to 'phone' - as raised in #31.

This PR:

• adds config to the test case in commit 85d92c9 to avoid the default fallback to 'phone'. The test then fails.

• adds a condition after all other attempts to match, to match a user agent string including iPhone as 'phone'. The test passes.

---

The following is how I can now receive 'phone' for iPhone, whilst still receiving null for other unknown strings.

device(
  'Mozilla/5.0 (iPhone; CPU iPhone OS 17_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko)', 
  {unknownUserAgentDeviceType: null}
).type

// 'phone'