Example sketch for one time measurements added

I added an example for one time measurements.

init has now a return value

The init function has now a return value which is 0 if the device is not connected.

Small bug in the example

While testing I commented both options for object definition in the example sketch.

Some minor changes

• Replaced #define by constexpr
• Emptied the constructors
• Replaced private by protected

typedef for enum definition was redundant

I have eliminated typedef in enum definition.

Use of multiple I2C busses possible

You can now pass a TwoWire object to the constructor. I have also updated the example sketch accordingly.

English documentation available

English documentation available:

https://wolles-elektronikkiste.de/en/bh1750fvi-gy-30-302-ambient-light-sensor

No change to the code.

keywords.txt added

I added keywords.txt

Update of library.properties

No real change to version 1.1.1. I just had just forgotten to update the version number in library properties before releasing 1.1.1. Corrected now.

Some changes to the folder structure

Some changes to the folder structure