Support option_add for HashMap options
Support option_add for HashMap options

Fixes #1407

Somasis/kakoune,mawww/kakoune,jkonecny12/kakoune,mawww/kakoune,Somasis/kakoune,occivink/kakoune,lenormf/kakoune,jkonecny12/kakoune,jjthrash/kakoune,jkonecny12/kakoune,casimir/kakoune,danr/kakoune,danr/kakoune,jjthrash/kakoune,occivink/kakoune,alexherbo2/kakoune,casimir/kakoune,danr/kakoune,Somasis/kakoune,alexherbo2/kakoune,mawww/kakoune,jjthrash/kakoune,mawww/kakoune,occivink/kakoune,lenormf/kakoune,jjthrash/kakoune,alexherbo2/kakoune,lenormf/kakoune,alexherbo2/kakoune,casimir/kakoune,danr/kakoune,casimir/kakoune,lenormf/kakoune,Somasis/kakoune,occivink/kakoune,jkonecny12/kakoune