Add CI workflows and ready for PIO publishing

[2bndy5]

I added 2 new CI workflows that tests the following examples:

• examples/Getting_Started_SimpleClient_Mesh
• examples/Getting_Started_SimpleServer_Mesh
• examples/InteractiveServer_Mesh
• examples/MQTT/mqtt_basic
• examples/MQTT/mqtt_basic_2
• examples/SimpleClient_Mesh

Any other examples require defining RF24_TAP or have architecture specific code. All examples' files have been re-formatted with Astyle formatter (as used by the Arduino IDE).

1. The Arduino CI workflow - tests above listed examples for most boards that other RF24 libs test compile for. I had to exclude the atmegang board because there isn't enough memory for any of the examples.
2. The PlatformIO CI workflow - tests the above listed examples on esp32 (tinyPico) and esp8266 (nodeMCU v2) boards.
   • when test compiling the tinypico, the compiler failed and complained about a pure virtual begin(uint16_t) in the Server parent class. So I added an overload that sets the private member _port to the uint16_t parameter and called the pre-existing RF24Server::begin(). This new overload only exists when ESP32 is defined.

As always I threw the badges in the README for quick glances from passersby.

When adding the library.json to the repo, I had to choose only 1 license as PIO doesn't support multiple entries in "license" field.

[2bndy5]

I suppose this lib could also get the Pico SDK treatment, but there are so many sources that need to be listed in the CMakeLists.txt that I'm putting it off (until I better understand the code here).

[2bndy5]

Is PIO integration not desired for this repo? I should've asked before I created that GH action workflow.