Reorganized the code, speed tweaks and updates to example sketches.

The major changes:

1. The source files were getting very big, so I split the .h and .cpp
   files into three .h files and three .cpp files. The files are
   still pretty big, but are now a little more manageable.

2. The Arduino's memory limitations are starting to really hinder
   expanding the library's feature set, so I split the header file into
   separate files for ESP (modes_esp.h) and Arduino (modes_arduino.h).
   Hopefully this will make it easer to add new features/effects for
   ESP devices, and not blow up the memory footprint for Arduino devices.

3. Updated the ws2812fx_patterns_web example sketch to use the
   async web server (ESPAsyncWebServer) instead of ESP8266WebServer,
   so the sketch now supports ESP8266 and ESP32.

4. removed support for the legacy AduinoJson v5 library in the
   ws2812fx_patterns_web example sketch. You must use the
   ArduinoJson v6 library.

5. Added the tester.zsh script to verify all the example sketches
   for Arduino, ESP8266 and ESP32 devices. Automated
   testing??? What a concept! :)

6. Refactored the modes for ESP devices, so the mode data is stored
   in a struct, and added an effect category to the struct. This
   should have been done long ago, but the tight coupling of Arduino
   and ESP code made it problematic. Hopefully this will spur more
   innovative GUI designs that don't just show one gigantic list
   of effects.

7. POTENTIALLY BREAKING CHANGE
   Changed the timing of the CHASE, TWINKLE_FADE, RUNNING, DYNAMIC
   and Fireworks effects to make them more consistent with the other
   effects. A speed setting of 1000 should give reasonable results
   for all effects. While this isn't strictly a breaking change,
   your speed settings for these effects might need to be tweaked
   to get the same animation rate you had before.

8. Refactored the rainbow_chase effect to be more efficient.