Remove arduino dependency

[luar123]

Remove Arduino dependency and add an example for platformio with espidf.
Without Arduino the I2C or SPI read and write functions need to be supplied together with delayus and millis.
Tested with and without Arduino framework.

This needs boschsensortec/Bosch-BME68x-Library#8

Library versions/locations in the example platformio.ini file should be updated when releasing.

Related: #47 #6

[TCB13]

How does this handle sleep scenarios on those boards? millis() are a controversial topic because they aren't kept between sleep in most sleep modes, however they do work in SLEEP_MODE_IDLE and the sensor doesn't work properly without correct timming.

[luar123]

Short answer: not at all
For arduino-framework there is no change, it will us arduinos implementation of millis().
On other platforms the user has to provide it. With esp-idf for example you can use esp_timer_get_time()which should keep the time in light sleep if I remember correctly. In deep sleep everything in ram is lost including the state, so this needs to be handled by the user anyway.