v0.621

Slight function documentation adjustment. Updated version of the library with the latest material added after reviewing section 6-2. Addition of functions "rotCntrClck45DegAboutZaxisXvec3", "projThroughXyPlaneXvec3", "projOntoXyPlaneXvec3", "scanRdcXmtx", with unit tests and extended tests. Built with version "zig-windows-x86_64-0.12.0".