Description of proposed changes

The GDAL creation option "SUFFIX=ADD" will append .hdr to the name, rather than replace the suffix. https://gdal.org/drivers/raster/envi.html

This addition will search for that extra naming convention for ENVI files and not miss the metadata.

Reminders

• Pass Codacy code review (green)
• Pass Circle CI test (green)
• Make sure that your code follows our style. Use the other functions/files as a basis.
• If modifying functionality, describe changes to function behavior and arguments in a comment below the function declaration.