fix: rules are at top level (not under overrides)

BREAKING CHANGE: the rules are provided at the top level,
instead of under an `overrides` property.
Providing the rules under the `overrides` property was never a good idea.
It prevents specifying which files the rules apply to (e.g. `[*.js, *.ts]`).
I apologize.
To migrate, make sure that your `extends` property is under an [`overrides` item][overrides].
An example is in the readme.
To help verify your configuration,
you could obtain a list of files that will be linted, this way:
`DEBUG=eslint:cli-engine npx eslint <path>`.

[overrides]: https://eslint.org/docs/latest/use/configure/configuration-files#how-do-overrides-work

closes #1149
closes #1088

Co-authored-by: Rostislav Simonik <rostislav.simonik@technologystudio.sk>

.eslintrc.json

@@ -1,6 +1,11 @@
 {
-  "extends": "./lib/index.js",
-  "parserOptions": {
-    "project": "./tsconfig.json"
-  }
+  "overrides": [
+    {
+      "files": ["*.js", "*.ts"],
+      "extends": "./lib/index.js",
+      "parserOptions": {
+        "project": "./tsconfig.json"
+      }
+    }
+  ]
 }

package.json

@@ -5,7 +5,7 @@
   "main": "lib/index.js",
   "scripts": {
     "compile": "tsc",
-    "lint": "eslint --ext .js,.ts .",
+    "lint": "eslint .",
     "editorconfig": "editorconfig-checker",
     "unit": "ava",
     "test": "run-s clean-artifacts editorconfig compile lint unit",

readme.md

@@ -49,21 +49,29 @@ npm install --save-dev \
 
 # Example config
 
-Here is an example `.eslintrc.js`:
+Here is an example `.eslintrc.js`.
+Pay close attention to the `files` property, because it [determines which files are linted][specifying-target-files-to-lint].
 
 ```js
 module.exports = {
-  extends: 'standard-with-typescript',
-  parserOptions: {
-    project: './tsconfig.json'
-  }
+  overrides: [
+    {
+      files: ['*.js', '*.jsx', '*.ts', '*.tsx'],
+      extends: 'standard-with-typescript',
+      parserOptions: {
+        project: './tsconfig.json'
+      }
+    }
+  ],
 }
 ```
 
 Note: Please read some important instructions regarding the `project` option [here](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/parser/README.md#configuration).
 
 There are [some more `parserOptions`](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/parser/README.md#configuration) you may care about.
 
+[specifying-target-files-to-lint]: https://eslint.org/docs/latest/use/configure/configuration-files#specifying-target-files-to-lint
+
 # Example command line usage:
 
 ```