Adding custom bitmaps to display

1. Use GIMP to create a small black-and-white image, and export it as an X BitMap (.xbm) file.
2. Copy the XBM file to the src/Display/Bitmaps/XBM folder. The filename can only contain alphanumeric characters and underscores, and cannot start with a number.
3. (Optional) Install the Python PNG library (requirements.txt).
4. Run the Python script src/Display/Bitmaps/Scripts/XBM-export.py to convert the XBM file to a format that the Arduino can read (.axbm) and to create an XBitmap from it.
5. (Optional) Run Doxygen again (in the doxygen folder) to include the new icon in the documentation.
6. You can now use the bitmap in your Arduino sketches, using the original file name (without .xbm).

mkdir -p docs/Doxygen
cd docs/Doxygen
python3 -m pip install -r ../../src/Display/Bitmaps/Scripts/requirements.txt
python3 ../../src/Display/Bitmaps/Scripts/XBM-export.py
cd ../../doxygen
doxygen