update readme

Author: RyosukeCla

README.md

@@ -2,16 +2,23 @@
 > jest json5 transformer
 
 ## Installation
+
+for jest >= 28
 ```
 $ npm i -D json5-jest
 ```
 
+for jest <= 27
+```
+$ npm i -D json5-jest@1
+```
+
 ## Jest integration
 Please append to package.json
 ```json
 "jest": {
   "transform": {
-    "^.+\\.json5?$": "json5-jest"
+    "^.+\\.json5$": "json5-jest"
   }
 }
 ```
@@ -20,17 +27,20 @@ or append to jest.config.js
 ```js
 module.exports = {
   transform: {
-    "^.+\\.json5?$": "json5-jest"
+    "^.+\\.json5$": "json5-jest"
   }
 };
 ```
 
 ## Requirements
 - node >= 6.9.0
 - npm >= 2.x
+- jest >= 28
 
 ## Licence
 MIT
 
 ## Contributers
 - [@MaxMellon](https://github.com/MaxMEllon)
+- [@wjbenfold](https://github.com/wjbenfold)
+- [@Duke242](https://github.com/Duke242)