* [MOD] Updated README

Author: nuxsmin

README.md

@@ -6,14 +6,29 @@ Plugin to use two factor based authentication with applications that generate TO
 
 Please, select the correct branch in order to download a sysPass compatible version:
 
-* sysPass v3: Master branch or 2.0
-* sysPass v2: 1.0 branch 
+* sysPass v3.1 --> Master or v2.1 branch
+* sysPass v3.0 --> 2.0 branch
+* sysPass v2 --> 1.0 branch 
 
 ---
 
-### v2 Installation
+### v2.1 Installation
 
-As told above, this version is only compatible with **sysPass v3** and it needs to be installed through **composer**.
+This version is only compatible with **sysPass v3.1** and it needs to be installed through **composer**.
+
+Please select the installation method depending on the instance type:
+
+* If you are running a **non-Docker** based instance:
+
+```composer require syspass/plugin-authenticator:^v2.1```
+
+* If you are running a **Docker** based instance, set `syspass/plugin-authenticator:^v2.1` value within an environment variable called `COMPOSER_EXTENSIONS`.
+ 
+---
+
+### v2.0 Installation
+
+This version is only compatible with **sysPass v3** and it needs to be installed through **composer**.
 
 Please select the installation method depending on the instance type:
 
@@ -25,7 +40,7 @@ Please select the installation method depending on the instance type:
 
 ---
 
-### v1 Installation
+### v1.0 Installation
 
 Please download the v1 branch files and unpack them into `.../inc/Plugins` directory.