Add to README how to load the extension from gh releases

Related to #588

Author: zalmoxisus

README.md

@@ -11,6 +11,7 @@
 
 ### 1. For Chrome
  - from [Chrome Web Store](https://chrome.google.com/webstore/detail/redux-devtools/lmhkpmbekcpmknklioeibfkpmmfibljd);
+ - download `extension.zip` from [last releases](https://github.com/zalmoxisus/redux-devtools-extension/releases), unzip, open `chrome://extensions` url and turn on developer mode from top left and then click; on `Load Unpacked` and select the extracted folder for use
  - or build it with `npm i && npm run build:extension` and [load the extension's folder](https://developer.chrome.com/extensions/getstarted#unpacked) `./build/extension`;
  - or run it in dev mode with `npm i && npm start` and [load the extension's folder](https://developer.chrome.com/extensions/getstarted#unpacked) `./dev`.