[codemirror_mode_extensions] add new nbextension

src/jupyter_contrib_nbextensions/nbextensions/codemirror_mode_extensions/codemirror_mode_extensions.yaml

@@ -0,0 +1,7 @@
+Type: Jupyter Notebook Extension
+Name: CodeMirror mode extensions
+Description: |
+  Extends some CodeMirror modes with extra features. Currently just adds
+  support for comment/uncomment and folding for octave/MATLAB mode.
+Main: main.js
+Compatibility: 4.x

src/jupyter_contrib_nbextensions/nbextensions/codemirror_mode_extensions/main.js

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+define(['codemirror/lib/codemirror'], function (CodeMirror) {
+    "use strict";
+    return {
+        load_ipython_extension : function () {
+            CodeMirror.extendMode('octave', {
+                lineComment: '%',
+                fold: 'indent',
+            });
+        }
+    };
+});