docs: update required node.js/eslint versions

Author: aladdin-add

README.md

@@ -16,8 +16,8 @@ Additional ESLint's rules for Node.js
 $ npm install --save-dev eslint eslint-plugin-n
 ```
 
-- Requires Node.js `>=8.10.0`
-- Requires ESLint `>=5.16.0`
+- Requires Node.js `>=12.22.0`
+- Requires ESLint `>=7.0.0`
 
 **Note:** It recommends a use of [the "engines" field of package.json](https://docs.npmjs.com/files/package.json#engines). The "engines" field is used by `n/no-unsupported-features/*` rules.