Add example markdown in the portal editor new section & fix MD view bug

- Example document contains common markdown syntax examples and is pre-loaded in the text area of a new section
- Also fix a bug in markdownView where the highlightjs showdown extension was not loading even though `code` was present in the markdown

Closes issue #1104

src/js/models/portals/PortalModel.js

@@ -16,11 +16,12 @@ define(["jquery",
         "models/CollectionModel",
         "models/Search",
         "models/filters/FilterGroup",
-        "models/Map"
+        "models/Map",
+        "text!templates/portals/editor/MarkdownExample.md",
     ],
     /** @lends PortalModel.prototype */
     function($, _, Backbone, gmaps, uuid, Filters, SolrResults, PortalSectionModel, PortalImage,
-        EMLParty, EMLText, CollectionModel, SearchModel, FilterGroup, MapModel) {
+        EMLParty, EMLText, CollectionModel, SearchModel, FilterGroup, MapModel, MarkdownExample) {
         /**
          * A PortalModel is a specialized collection that represents a portal,
          * including the associated data, people, portal descriptions, results and
@@ -85,6 +86,11 @@ define(["jquery",
                 });
             },
 
+            /**
+             * The default text to use in the markdown example in a new section
+            */
+            markdownExample: MarkdownExample,
+
             /**
              * Overrides the default Backbone.Model.initialize() function to
              * provide some custom initialize options
@@ -1238,7 +1244,7 @@ define(["jquery",
                       newSection.set({
                         label: newSectionLabel,
                         content: new EMLText({
-                                      markdown: "Add some content here.",
+                                      markdown: this.markdownExample,
                                       type: "content"
                                   })
                       });

src/js/templates/portals/editor/MarkdownExample.md

@@ -0,0 +1,48 @@
+Replace this example with your content. Styling using markdown is supported.
+
+# Level 1 Header
+
+Markdown is a simple way to format text.
+
+## Level 2 Header
+
+For example, *this text will be italic* and **this text will be bold**. Here is a link to [DataOne](https://www.dataone.org), and here is an equation written using the TeX language: $$ y =X\beta + \epsilon $$.
+
+Add an image like so: ![DataOne logo](https://www.dataone.org/sites/default/files/d1-logo-v8_aligned_left.png)
+
+Show in-line code using `single backticks`, or show it as a separate block using triple backticks:
+
+```r
+my_string <- "Check out the code I wrote"
+print(my_string)
+```
+
+Here is how to make a table:
+| Tables | Are | Cool  |
+| ------ | --- | ----- |
+| x      | a   | $1600 |
+| y      | b   |   $12 |
+| z      | c   | $1600 |
+
+The following is an unordered list:
+* List item a
+* List item b
+* List item c
+    * You can create nested lists by indenting list items by four spaces.
+    * Sub-item 2
+
+This is a numbered list:
+1. First
+2. Second
+3. Third
+
+To quote some text, just start a line with a `>` character. In the words of Grace Hopper:
+> information is more valuable than the hardware which processes it.
+
+You can even add emojis :smile:!
+
+### More help with markdown
+
+- [Markdown reference](https://commonmark.org/help/)
+- [Ten minute tutorial](https://commonmark.org/help/tutorial/)
+- For a longer example where you can also preview the results, checkout the [Showdown Live Editor](http://demo.showdownjs.com/)

src/js/views/MarkdownView.js

@@ -99,7 +99,7 @@ define([    "jquery", "underscore", "backbone",
             // ===== the regular expressions used to test whether showdown extensions are required ===== //
             // note: these expressions test the *markdown* and *not* the html
 
-            var regexHighlight  = new RegExp("'.*'"), // too general?
+            var regexHighlight  = new RegExp("`.*`"), // too general?
                 regexDocbook    = new RegExp("<(title|citetitle|emphasis|para|ulink|literallayout|itemizedlist|orderedlist|listitem|subscript|superscript).*>"),
                 // for bootstrap: test for tables, directly from showdown/src/subParsers/makehtml/tables.js
                 // if we add more bootstrap classes, this will become more complicated since we have to test the markdown before the initial parse