Added ability to create a dashed vertical line in arrays, using ':' (#1395)

* hacked together a dashed vertical bar

* Updated tests and spec.

* tidied up the screenshot template for arrays

* added the vertical lines at the end back

* Updated screenshots for arrays

src/environments/array.js

@@ -282,6 +282,15 @@ const htmlBuilder = function(group, options) {
                 separator.style.verticalAlign =
                     -(totalHeight - offset) + "em";
 
+                cols.push(separator);
+            } else if (colDescr.separator === ":") {
+                const separator = buildCommon.makeSpan(
+                    ["vertical-separator", "vs-dashed"], [], options
+                );
+                separator.style.height = totalHeight + "em";
+                separator.style.verticalAlign =
+                    -(totalHeight - offset) + "em";
+
                 cols.push(separator);
             } else {
                 throw new ParseError(
@@ -465,6 +474,11 @@ defineEnvironment({
                     type: "separator",
                     separator: "|",
                 };
+            } else if (ca === ":") {
+                return {
+                    type: "separator",
+                    separator: ":",
+                };
             }
             throw new ParseError(
                 "Unknown column alignment: " + node.value,