[docs] update v2 sidebar links to correctly go to v2 docs

docs/v2/_sidebar.md

@@ -1,34 +1,30 @@
 - Getting started
- - [Initial setup](/initial-setup)
- - [Installation - iOS](/installation-ios)
- - [Installation - Android](/installation-android)
- - [Usage](/usage)
- - [Migration Guide](/migration-guide)
+ - [Initial setup](/v2/initial-setup)
+ - [Installation - iOS](/v2/installation-ios)
+ - [Installation - Android](/v2/installation-android)
+ - [Usage](/v2/usage)
+ - [Migration Guide](/v2/migration-guide)
 
 - Contributing
- - [Guidelines](/contributing/guidelines)
- - [Testing](/contributing/testing)
-
-- Core
- - [App](/core/app)
- - [Firebase](/core/firebase)
+ - [Guidelines](/v2/contributing/guidelines)
+ - [Testing](/v2/contributing/testing)
 
 - Modules
- - [Admob](/modules/admob)
- - [Analytics](/modules/analytics)
- - [Authentication](/modules/authentication)
- - [Cloud Messaging](/modules/cloud-messaging)
- - [Crash Reporting](/modules/crash)
- - [Database](/modules/database)
- - [Remote Config](/modules/config)
- - [Storage](/modules/storage)
- - [Transactions](/modules/transactions)
- - [Performance Monitoring](/modules/perf)
+ - [Admob](/v2/modules/admob)
+ - [Analytics](/v2/modules/analytics)
+ - [Authentication](/v2/modules/authentication)
+ - [Cloud Messaging](/v2/modules/cloud-messaging)
+ - [Crash Reporting](/v2/modules/crash)
+ - [Database](/v2/modules/database)
+ - [Remote Config](/v2/modules/config)
+ - [Storage](/v2/modules/storage)
+ - [Transactions](/v2/modules/transactions)
+ - [Performance Monitoring](/v2/modules/perf)
 
 - Other
-  - [Usage with Redux](/redux)
+  - [Usage with Redux](/v2/redux)
   - [Project Board](https://github.com/invertase/react-native-firebase/projects)
-  - [FAQs / Troubleshooting](/faqs)
+  - [FAQs / Troubleshooting](/v2/faqs)
   - [Examples](https://github.com/invertase/react-native-firebase-examples)
   - [Chat](https://discord.gg/t6bdqMs)
   - [Gitter](https://gitter.im/invertase/react-native-firebase)