BT A2DP source supports 48000 Hz sample rate

[anp59]

Hi schreibfaul1,
First of all a big thank you for your tireless work on the ESP32-audioI2S library.
When the change to the 48000 Hz I2S sample rate was made a few weeks ago, I was not so happy as I was about to use the Bluetooth source function with the A2DP library
in a project.
After some searching, I came across a solution for the BT-Lib to be able to work with 48000 Hz in source mode.
This enables a simultaneous 48000 Hz I2S sample rate with the ESP32-audioI2S library and ESP32-Bluetooth, without resampling the audio data again.
A sample PIO project is available at https://github.com/anp59/I2S-Bluetooth-Transmitter for those interested.
The adjustments to the BT component in the ESP-IDF can be found at https://github.com/anp59/I2S_BluetoothTransmitter_48k
Have fun trying it out.