Update 5.2.0

• Added support for Teensy (#175)
• Allow SPItransfer to be overridden by subclasses (by @caveman99)
• [SX126x] Added LR-FHSS registers
• [SX127x] Fixed RF switch not actuated in continuous Rx mode (#531)
• [SX126x] Fixed default frequency deviation for SX1262 (#522)
• [Hell] Added method to invert text color (#529)
• [Morse] Use out of band tone for space in AFSK mode (#529)
• [SX127x] added setCrcFiltering() (by @matthias-bs)
• [CC1101] Fixed incorrect parameter documentation (#523)
• [CC1101] Fixed Tx buffer flushed on Rx timeout (#520)
• [SX126x] Fixed swapped IQ inversion fix branches (#516)
• [SX126x] Enable timeout to generate IRQ event
• [SX127x] Use RSSI interrupt and disable AFC (#505)
• [CC1101] Fixed RSSI/LQI always returning incorrect values (#504)
• [RF69] Call setRxBandwidth again if setOOK is called (by @loopj)
• [SX126x] Set initial BW to 500 kHz for LLCC68 (#502)
• Added support for MegaCore boards
• [CC1101] Fixed incorrect fabs brackets (#490)
• Introduce asynchronous reception and transmission for CC1101 (by @obones)
• [SX127x] Added missin ISR flag for ESP32/ESP8266
• [SX128x] Add method to support SX128x Manual Gain Mode. (by @JasonRJ)
• [SX126x] Fixed CubeCell predefined module macro (#479)