implemented new way of adding extra languages to note type picker

src/routes/api/custom_code_mime_types.js

@@ -0,0 +1,24 @@
+"use strict";
+
+const attributesService = require('../../services/attributes');
+const log = require('../../services/log');
+
+async function get() {
+    const notes = await attributesService.getNotesWithLabel('codeMimeTypes');
+    let merged = [];
+
+    for (const note of notes) {
+        try {
+            merged = merged.concat(await note.getJsonContent());
+        }
+        catch (e) {
+            log.error(`Cannot merge mime types from note=${note.noteId}: ${e.message}`);
+        }
+    }
+
+    return merged;
+}
+
+module.exports = {
+    get
+};