[yaml mode] Add lineComment property
[yaml mode] Add lineComment property

Closes #5248

hackmdio/CodeMirror,namin/CodeMirror,SidPresse/CodeMirror,dperetti/CodeMirror,notepadqq/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,namin/CodeMirror,ficristo/CodeMirror,pabloferz/CodeMirror,namin/CodeMirror,mtaran-google/CodeMirror,notepadqq/CodeMirror,nightwing/CodeMirror,SidPresse/CodeMirror,wingify/CodeMirror,mtaran-google/CodeMirror,ficristo/CodeMirror,dperetti/CodeMirror,nightwing/CodeMirror,thomasjm/CodeMirror,notepadqq/CodeMirror,thomasjm/CodeMirror,hackmdio/CodeMirror,jkaplon/CodeMirror,mtaran-google/CodeMirror,codio/CodeMirror,wingify/CodeMirror,wingify/CodeMirror,jkaplon/CodeMirror,jkaplon/CodeMirror,pabloferz/CodeMirror,ficristo/CodeMirror,dperetti/CodeMirror,pabloferz/CodeMirror,codio/CodeMirror,SidPresse/CodeMirror,thomasjm/CodeMirror,codio/CodeMirror