docs: add some dev info about ssp-assets-base to help new developers find things#2235

tvdijen merged 2 commits intosimplesamlphp:simplesamlphp-2.3simplesamlphp/simplesamlphp:simplesamlphp-2.3from

monkeyiq:2024/sep/docs-ssp-assets-base-infomonkeyiq/simplesamlphp:2024/sep/docs-ssp-assets-base-infoCopy head branch name to clipboard