docs(query-interface): addColumn example (#9366)

lib/query-interface.js

@@ -508,6 +508,11 @@ class QueryInterface {
   /**
   /**
    * Add a new column into a table
    * Add a new column into a table
    *
    *
+   * ```js
+   * queryInterface.addColumn('tableA', 'columnC', Sequelize.STRING, {
+   *    after: 'columnB' // after option is only supported by MySQL
+   * });
+   * ```
    * @param {String} table     Table to add column to
    * @param {String} table     Table to add column to
    * @param {String} key       Column name
    * @param {String} key       Column name
    * @param {Object} attribute Attribute definition
    * @param {Object} attribute Attribute definition