Update README.md

Update readme for 2.1.0 release

README.md

@@ -13,7 +13,7 @@ This extension provides the `#mermaid` parser function to support the generation
 ## Requirements
 
 - PHP 5.6 or later
-- MediaWiki 1.27 or later
+- MediaWiki 1.31 or later
 
 ## Installation
 
@@ -35,15 +35,15 @@ If you do not have a "composer.local.json" file yet, create one and add the foll
 ```
 {
 	"require": {
-		"mediawiki/mermaid": "~2.0"
+		"mediawiki/mermaid": "~2.1"
 	}
 }
 ```
 
 If you already have a "composer.local.json" file add the following line to the end of the "require"
 section in your file:
 
-    "mediawiki/mermaid": "~2.0"
+    "mediawiki/mermaid": "~2.1"
 
 Remember to add a comma to the end of the preceding line in this section.