Added Breaking changes & Module Entity Extensibility sections

docs/en/Blog-Posts/2020-08-20 v3_1_Release/Post.md

@@ -57,6 +57,18 @@ If you already have a solution and want to use/test the latest RC/Preview versio
 
 > Note that the `abp switch-to-preview` command was being used to switch to nightly builds before the v3.1. Now, you should use the `abp switch-to-nightly` for [nightly builds](https://docs.abp.io/en/abp/latest/Nightly-Builds).
 
+## Breaking Changes / Special Notes
+
+### ABP & ABP Commercial
+
+* If you are using **EF Core**, you may need to **add a new migration** after upgrading the packages. Just run the standard "Add-Migration" command, check the generated migration code and execute the "Update-Database" command to apply changes to the database.
+* If you have implemented **social/external logins** for your MVC / Razor Page UI application before, you may want to check [this issue](https://github.com/abpframework/abp/issues/4981). We made some improvements and changes that you may want to take action for your application. Beginning from v3.1, the users created their accounts via social login can still set a local password to login with local username/email & password.
+
+### ABP Commercial Only
+
+* We've **moved favicons** into `/wwwroot/images/favicon/` folder for the ASP.NET Core **MVC / Razor Page UI** applications. There are 10 favicon related files (including the `favicon.ico`) under this directory to better work with different browser and cases. You can create a new application to check this folder and copy the files into your own application. Then you can customize the icons for your own brand.
+* Removed direct **Twitter & Facebook social login integrations** from the [account module](https://commercial.abp.io/modules/Volo.Account.Pro), for **MVC / Razor Pages UI**. Follow [this documentation](https://github.com/abpframework/abp/blob/dev/docs/en/Authentication/Social-External-Logins.md) to easily add social logins to your applications if you need. The account module provides all the infrastructure to handle social/external logins, you just need to configure it.
+
 ## What's New with the ABP Framework 3.1 RC.1
 
 ### Angular Service Proxies
@@ -167,6 +179,10 @@ The new [Security Log System](https://github.com/abpframework/abp/issues/4492) (
 
 Implemented [AWS](https://github.com/abpframework/abp/blob/dev/docs/en/Blob-Storing-Aws.md) and [Aliyun](https://github.com/abpframework/abp/blob/dev/docs/en/Blob-Storing-Aliyun.md) providers for the [BLOB storing](https://docs.abp.io/en/abp/latest/Blob-Storing) system with this version.
 
+### Module Entity Extensibility
+
+We had introduced a entity extension system that allows to add new properties to existing entities of depended modules by a simple configuration. When you add a new property, it appears on the create, edit and list views on the UI and created a new field in the related database table. We've implemented this system for the identity and tenant management modules, so you can extend entities of these modules. See [the documentation](https://github.com/abpframework/abp/blob/dev/docs/en/Module-Entity-Extensions.md).
+
 ### Other Features / Highlights
 
 Here, some other highlights from this release;