Update to auto generate meta description based on content in publish note and slide

lib/models/note.js

@@ -260,6 +260,9 @@ module.exports = function (sequelize, DataTypes) {
                 if (!title) title = "Untitled";
                 return title;
             },
+            generateDescription: function (markdown) {
+                return markdown.substr(0, 100).replace(/(?:\r\n|\r|\n)/g, ' ');
+            },
             decodeTitle: function (title) {
                 var decodedTitle = LZString.decompressFromBase64(title);
                 if (decodedTitle) title = decodedTitle;