Added v5 deprecation message to FAQs section

Solves invertase#3791 using a comment from invertase#3833

Author: andersonaddo

docs/faqs-and-tips.md

@@ -13,9 +13,12 @@ If you come across a discussion that results in great advice that can benefit ma
 
 # FAQs
 
-Here are some commonly encountered problems:
+### I need help with [anything regzrdinf v5 of react-native-firebase]
+RNFB v5 is now deprecated and unsupported. There's been over a year's grace period provided to migrate to v6, so moving forward maintainers probably won't pay much attention to issues regarding v5. Understandably, upgrading to v6 can take effort, but staying on v5 probably isn't a great choice for the long-term health of your project.
+Lots of the breaking changes that were introduced were either due to upstream deprecations in the official SDKs, or to simply make the package more stable and more representative of how the actual SDKs work.
+The longer you stay on v5, the more your project will be out of sync with the official SDKs, unfortunately. Couple that with the fact that it's no longer actively supported, and that's trouble looming over the horizon for your project.
 
-[TODO]
+We highly recommend taking the necessary pains to update to v6. 
 
 # Tips
  - Advice on supporting multiple environments (for example, dev, prod, maybe also staging, qa) for your React Native Firebase App: [#3504]( https://github.com/invertase/react-native-firebase/issues/3504)