Return which I2C Address is in use

[SV-Zanshin]

Is your feature request related to a problem? Please describe.
Since the BME680 can have two possible I2C addresses, it would be good to know which address is being used by the library instance

Describe the solution you'd like
Add a new function, "getI2CAddress()" which will return the current BME680 I2C Address

Describe alternatives you've considered
The alternative is to expose the internal "I2CAddress" variable, but if that is done then the user can change the I2C address determined during instantiation and break the library.

Additional context
none.

[SV-Zanshin]

Created a new function "getI2CAddress()" which returns the current I2C address of the BME680.

Implemented as part of Version v1.0.8