docs: add info on where data is stored (#912)

This is a docs change and relates to issue #905 - adding information on
where data is stored.

I placed it under the advanced category in the sidebar.

Author: jackbridger

website/docs/advanced/Where-data-stored.md

@@ -0,0 +1,11 @@
+---
+id: where_data_stored
+title: Where your data is stored
+sidebar_label: Where data is stored
+---
+
+* **Android** - SQLite
+* **iOS** - small values (not exceeding 1024 characters) are serialized and stored in a common `manifest.json` file, while larger values are stored in individual, dedicated files (named as MD5 hashed `key`)
+* **macOS** - Same as iOS
+* **Web** - window.localStorage
+* **Windows** - SQLite

website/sidebars.js

@@ -1,7 +1,7 @@
 module.exports = {
   docs: {
     'Getting started': ['install', 'usage', 'api', 'limits'],
-    Advanced: ['advanced/next', 'advanced/jest', 'advanced/brownfield', 'advanced/backup', 'advanced/executor', 'advanced/db_size'],
+    Advanced: ['advanced/next', 'advanced/jest', 'advanced/brownfield', 'advanced/backup', 'advanced/executor', 'advanced/db_size','advanced/where_data_stored'],
     Debugging: ['debugging/communityPackages'],
     Help: ['help/troubleshooting'],
   },