Update CodeMirror to version 5.49.0 (#8381)

* Update CodeMirror to version 5.49.0

* Update CodeMirror versions in librejs and VERSIONS

public/vendor/plugins/codemirror/addon/fold/markdown-fold.js

@@ -0,0 +1,49 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: https://codemirror.net/LICENSE
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    mod(require("../../lib/codemirror"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+"use strict";
+
+CodeMirror.registerHelper("fold", "markdown", function(cm, start) {
+  var maxDepth = 100;
+
+  function isHeader(lineNo) {
+    var tokentype = cm.getTokenTypeAt(CodeMirror.Pos(lineNo, 0));
+    return tokentype && /\bheader\b/.test(tokentype);
+  }
+
+  function headerLevel(lineNo, line, nextLine) {
+    var match = line && line.match(/^#+/);
+    if (match && isHeader(lineNo)) return match[0].length;
+    match = nextLine && nextLine.match(/^[=\-]+\s*$/);
+    if (match && isHeader(lineNo + 1)) return nextLine[0] == "=" ? 1 : 2;
+    return maxDepth;
+  }
+
+  var firstLine = cm.getLine(start.line), nextLine = cm.getLine(start.line + 1);
+  var level = headerLevel(start.line, firstLine, nextLine);
+  if (level === maxDepth) return undefined;
+
+  var lastLineNo = cm.lastLine();
+  var end = start.line, nextNextLine = cm.getLine(end + 2);
+  while (end < lastLineNo) {
+    if (headerLevel(end + 1, nextLine, nextNextLine) <= level) break;
+    ++end;
+    nextLine = nextNextLine;
+    nextNextLine = cm.getLine(end + 2);
+  }
+
+  return {
+    from: CodeMirror.Pos(start.line, firstLine.length),
+    to: CodeMirror.Pos(end, cm.getLine(end).length)
+  };
+});
+
+});