docs: use eslint v8(latest)

Author: aladdin-add

README.md

@@ -8,7 +8,7 @@ React specific linting rules for `eslint`
 # Installation
 
 ```sh
-$ npm install eslint@7 eslint-plugin-react --save-dev
+$ npm install eslint@8 eslint-plugin-react --save-dev
 ```
 
 It is also possible to install ESLint globally rather than locally (using npm install eslint --global). However, this is not recommended, and any plugins or shareable configs that you use must be installed locally in either case.