Add the following file names to the root /.gitignore file:

# Ignore macOS files
.DS_Store
.DocumentRevisions-V100
.fseventsd
.Spotlight-V100
.TemporaryItems
.Trashes
.VolumeIcon.icns
.com.apple.timemachine.donotpresent

# ignore Windows files
Desktop.ini
Thumbs.db