Update .js files for markdown rendering:

- Add comments in each file indicatint where the
  original copy come frome, what is the version,
  our customizations, etc.
- Use eslint with es5 plugin and update:
    markdown-it-toc.js
    markdown-it-mathjax.js
    markdown-it-ins-del.js
    md.js
- Use Babel to convert ES6 scirpts to ES5:
    markdown-it-highlightjs.js
- Add `.eslintrc.js`.

Author: cslzchen

.eslintrc.js

@@ -0,0 +1,18 @@
+module.exports = {
+    "plugins" : ["es5"],
+    "extends" : "eslint:recommended",
+    "rules": {
+        "indent": ["error", 4],
+        "linebreak-style": ["error", "unix"],
+        "quotes": ["error", "double"],
+        "semi": ["error", "always"],
+        "no-undef": 1,
+        "no-useless-escape": 1,
+        "no-unused-vars": 1,
+        "no-redeclare": 1
+    },
+    "env": {
+        "browser": true,
+    },
+}
+

mfr/extensions/md/static/js/markdown-it-highlightjs.js

@@ -1,50 +1,72 @@
-;(function (root, factory) {
-  if (typeof exports === 'object') {
-    module.exports = factory()
-  } else {
-    root.markdownitHightlightjs = factory()
-  }
-})(this, function () {
+/**
+ * Preset to use highlight.js with markdown-it.
+ *
+ * Original Copy: https://github.com/valeriangalliat/markdown-it-highlightjs/tree/v3.0.0/index.js
+ *      The above link gives a 404. Here is my forked copy and Babel-converted ES5 version:
+ *      (ES6) https://github.com/cslzchen/markdown-it-highlightjs/blob/release/3.0.0/index.js
+ *      (ES5) https://github.com/cslzchen/markdown-it-highlightjs/blob/release/3.0.0/index.es5.js
+ * Version: https://github.com/valeriangalliat/markdown-it-highlightjs/releases/tag/v3.0.0
+ * Changes: 1. Use https://babeljs.io/repl/ to convert ES6 to ES5, 2. Use `window` instead of `require`
+ */
 
-const maybe = f => {
-  try {
-    return f()
-  } catch (e) {
-    return false
-  }
-}
-
-// Highlight with given language.
-const highlight = (code, lang) =>
-  maybe(() => hljs.highlight(lang, code, true).value) || ''
-
-// Highlight with given language or automatically.
-const highlightAuto = (code, lang) =>
-  lang
-    ? highlight(code, lang)
-    : maybe(() => hljs.highlightAuto(code).value) || ''
-
-// Wrap a render function to add `hljs` class to code blocks.
-const wrap = render =>
-  function (...args) {
-    return render.apply(this, args)
-      .replace('<code class="', '<code class="hljs ')
-      .replace('<code>', '<code class="hljs">')
-  }
-  var defaults = {
-    auto: true,
-    code: true
-  }
-
-  return function(md, opts){
-    opts = Object.assign({}, defaults, opts)
-
-    md.options.highlight = opts.auto ? highlightAuto : highlight
-    md.renderer.rules.fence = wrap(md.renderer.rules.fence)
-
-    if (opts.code) {
-      md.renderer.rules.code_block = wrap(md.renderer.rules.code_block)
+(function (root, factory) {
+    if (typeof exports === "object") {
+        module.exports = factory();
+    } else {
+        root.markdownitHightlightjs = factory();
     }
-  }
+})(this, function () {
+
+    "use strict";
+
+    var maybe = function maybe(f) {
+        try {
+            return f();
+        } catch (e) {
+            return false;
+        }
+    };
+
+    // Highlight with given language.
+    var highlight = function highlight(code, lang) {
+        return maybe(function () {
+            return hljs.highlight(lang, code, true).value;
+        }) || "";
+    };
+
+    // Highlight with given language or automatically.
+    var highlightAuto = function highlightAuto(code, lang) {
+        return lang ? highlight(code, lang) : maybe(function () {
+            return hljs.highlightAuto(code).value;
+        }) || "";
+    };
+
+    // Wrap a render function to add `hljs` class to code blocks.
+    var wrap = function wrap(render) {
+        return function () {
+            for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
+                args[_key] = arguments[_key];
+            }
+
+            return render.apply(this, args).replace("<code class=\"", "<code class=\"hljs ").replace("<code>", "<code class=\"hljs\">");
+        };
+    };
+
+    var defaults = {
+        auto: true,
+        code: true
+    };
+
+    return function(md, opts) {
+
+        opts = Object.assign({}, defaults, opts);
+
+        md.options.highlight = opts.auto ? highlightAuto : highlight;
+        md.renderer.rules.fence = wrap(md.renderer.rules.fence);
+
+        if (opts.code) {
+            md.renderer.rules.code_block = wrap(md.renderer.rules.code_block);
+        }
+    };
 
-})
+});