Add invertible-grammar, take over sexp-grammar
Add invertible-grammar, take over sexp-grammar

Take over `sexp-grammar` in order to get notifications about the package.
massysett/stackage,fimad/stackage,mrkkrp/stackage,ethercrow/stackage,spencerjanssen/stackage,jonschoning/stackage,asr/stackage,Daniel-Diaz/stackage,mstksg/stackage,clinty/stackage,fpco/stackage,soenkehahn/stackage,michalkonecny/stackage,Shimuuar/stackage,athanclark/stackage,peti/stackage,simonmichael/stackage,lwm/stackage,creichert/stackage,mgajda/stackage,int-index/stackage,stackbuilders/stackage,wereHamster/stackage,iand675/stackage