Add more pictures, and remove all locally defined entities from index.docbook. Compressed
the images used in the first two chapters to 8-bit color using pngquant.
IMPORTANT NOTE: I have recently updated "contributor.entities" and "general.entities"
in the central "kdoctools" repository (src/customization/entities/), so these .docbook
files (index, intro, and getting-started) will work locally if, and only if, you update
those two files in /usr/share/kf5/kdoctools/customization/entities/.