Extensions for Twinkly Squares (2nd Generation), auto discovery, mocks, better example-code

[JanDiederich]

Hi, I had to make some changes to make the library work for me, please let me explain why I did what:

• Different fields in DeviceInfoResponse: The Twinkly Squares 2nd Generation I use this with, miss a field (flash_size) and have a field (pwr), which I had to make Optional (flash_size) and add as Optional (pwr).
• For better handling in complex processes, I made some struct's clone-able, and in one simple case copy-able.
• For automatic, continues discovery of devices in the background, so it can be detected if devices are added, I added PartialEq, Eq derivatives, and PartialOrd implementation. The last one to make it easier to compare lists, which have the same order. I need to figure out if a device is a actually new -- or just a new IP-Address, longer uptime, etc.
• The Twinkly Squares aren't that cheap, so I added methods to create mock devices for development.
• I converted the Hardware-Version, which was an arbitrary, anonymous u32, to HardwareVersion, because the number is actually not arbitrary and can only be handled with certainty for the numbers 1 to 3.
• I updated the example code in your README.md for the device control to run Out-of-the-Box. Meaning: You don't have to know the IP-Address and MAC-Address of your device(s). Just run the example. This feels much more comfortable.

All in all I'm very thankful for your work. Big thanks.

If you see problems in my Pull-Request, please explain, I will fix them.

[cgorski]

Hi! Thanks for the code! I should be able to look this over soon.

[cgorski]

Merged - much appreciated! I only modified this with changed proposed by fmt and clippy. I have since updated the github actions config so that these will automatically run on future pull-requests.

[JanDiederich]

Big thanks for including my Pull-Request.