docs: clarify which versions of ESLint are supported (#1073)

Co-authored-by: Brad Zacher <brad.zacher@gmail.com>

README.md

@@ -27,6 +27,7 @@
 - [How do I configure my project to use typescript-eslint?](#how-do-i-configure-my-project-to-use-typescript-eslint)
 - [Package Versions](#package-versions)
 - [Supported TypeScript Version](#supported-typescript-version)
+- [Supported ESLint version](#supported-eslint-version)
 - [License](#license)
 - [Contributors](#contributors)
 - [Contributing Guide](#contributing-guide)
@@ -246,6 +247,10 @@ If you use a non-supported version of TypeScript, the parser will log a warning
 
 <br>
 
+## Supported ESLint version
+
+See the value of `eslint` declared in `@typescript-eslint/eslint-plugin`'s [package.json](./packages/eslint-plugin/package.json).
+
 ## License
 
 TypeScript ESLint inherits from the the original TypeScript ESLint Parser license, as the majority of the work began there. It is licensed under a permissive BSD 2-clause license.