Added (after:), a shorthand form of (event:) similar to that in Chapbook.
Notable about this macro design, unlike its (event:) form, is that it contains an optional "skip" parameter similar to that for (t8n-skip:). Also: * Fixed a bug in the previous commit (which should've included <tw-story> as its exception). * Fiddled with various parts of the documentation. * Tweaked (palette:) to produce less dark link text whenever the produced normal text colour is rather dark.