How to let Notepadqq see a new mode in src/editor/libs/codemirror/mode/<newmode>.

1. Make sure that the CodeMirror submodule points at the right commit (usually a branch in the form of [CodeMirrorVersion]-nqq)
2. In src/editor/classes/Languages.js, extend this.languages with the new language information
3. In src/editor/index.html, add a link to the javascript file within src/editor/libs/codemirror/mode/<newmode>