12.1 stable

New specifications:

• PJDL v4.1 includes the maximum range of each mode experimentally determined by @jdaandersj
• PJON v3.2 is updated with more detailed description of the model and its procedures

Changelog:

• PJONLocal class implements a subset of the PJON protocol's features and it was developed to enable PJON networking on very limited microcontrollers, where even few bytes of ram can make a difference
• MQTTTranslate strategy can connect PJON networks and more standard applications with each other using MQTT, developed by @fredilarsen
• SoftwareBitBang maximum range is 800-2000m, experimentally determined by @jdaandersj
• SoftwareBitBang ATmega328PB support added by @willie68 (#309)
• PJONVirtualBusRouter detection of missing/moved devices added by @fredilarsen
• ESPNOW PlatformIO examples added by @justoke
• Enhanced routing documentation

Bugfix:

• DualUDP back-off frequency reduced to avoid performance loss by @fredilarsen
• DualUDP peformance loss on ESP8266 fixed by @fredilarsen (0325299)

Backward compatibility is preserved.