Building KDE software with kde-builder - kde-builder.yaml needs docs for all fields

Add a little text and link on the page to assist people new to kde-builder with commonly used options Ex: --ignore-projects I don't know if there are other flags people who have used kdesrc-build that might also be useful

Link from https://develop.kde.org/docs/getting-started/building/kde-builder-compile/ to the more complete config doc

I specifically had been looking for what replaced ignore-modules. I did find that it's ignore-projects and takes a list.