docs: introduce CHANGELOG.md, update README with instructions for flat config

Author: jackw

CHANGELOG.md

@@ -0,0 +1,105 @@
+# Grafana Eslint config changelog
+
+## 8.0.0
+
+- **Breaking**: Migrate dependencies to peerDependencies. Please make sure to install peerDependencies when using this package.
+- Add flat config for Eslint 9 support.
+
+## 7.0.0
+
+- Bump dependencies.
+
+## 6.0.1
+
+- Remove @typescript-eslint/explicit-member-accessibility rule.
+
+## 6.0.0
+
+- Bump dependencies.
+
+## 5.1.0
+
+- Bump dependencies to support Node 18.
+
+## 5.0.0
+
+- Add no-var rule.
+
+## 4.0.0
+
+- Bump dependencies.
+
+## 3.0.0
+
+- Remove eslint-plugin-prettier.
+
+## 2.5.2
+
+- Bump dependencies.
+
+## 2.5.1
+
+- Update eslint-config-prettier and eslint-plugin-jsdoc.
+- Report react-hooks/exhaustive-deps as error.
+
+## 2.5.0
+
+- Update typescript to 4.3.4.
+- Update @typescript-eslint/eslint-plugin and @typescript-eslint/parser.
+
+## 2.4.0
+
+- Update typescript to 4.2.4.
+- Update @typescript-eslint/eslint-plugin and @typescript-eslint/parser.
+
+## 2.3.0
+
+- Update Eslint dependency.
+
+## 2.2.1
+
+- Bump dependencies.
+
+## 2.2.0
+
+- Add no-duplicate-imports.
+
+## 2.1.1
+
+- Update eslint-plugin-prettier.
+
+## 2.1.0
+
+- Update Prettier and eslint-config-prettier.
+
+## 2.0.6
+
+- Adds eslint-plugin-react with recommended setings enabled.
+
+## 2.0.5
+
+- Allow console info statements.
+
+## 2.0.4
+
+- Bump eslint-plugin-react-hooks to 4.1.2.
+
+## 2.0.3
+
+- Pin dependencies to specific versions.
+
+## 2.0.2
+
+- Migrate peerDependencies to dependencies.
+
+## 2.0.1
+
+- Bump dependencies.
+
+## 2.0.0
+
+- Bump dependencies.
+
+## 1.0.0-rc1
+
+Initial release candidate.

README.md

@@ -22,7 +22,7 @@ Don't forget to install peerDependencies.
 npm info "@grafana/eslint-config@latest" peerDependencies
 ```
 
-If using **npm 5+**, use this shortcut
+If using **npm 5+**, use this command:
 
 ```sh
 npx install-peerdeps --dev @grafana/eslint-config
@@ -31,7 +31,9 @@ npx install-peerdeps --dev @grafana/eslint-config
 If using **yarn**, you can also use the shortcut described above if you have npm 5+ installed on your machine, as the command will detect that you are using yarn and will act accordingly.
 Otherwise, run `npm info "@grafana/eslint-config@latest" peerDependencies` to list the peer dependencies and versions, then run `yarn add --dev <dependency>@<version>` for each listed peer dependency.
 
-## Usage
+## Configuration (legacy: .eslintrc\*)
+
+Extend our configuration to get reasonable defaults:
 
 ```json
 {
@@ -41,6 +43,58 @@ Otherwise, run `npm info "@grafana/eslint-config@latest" peerDependencies` to li
 
 It will automatically handle `*.(js|ts|tsx)` files.
 
+## Configuration (new: eslint.config.js)
+
+From v8.21.0, Eslint supported a new flat config system where `eslint.config.js` replaces `.eslintrc*` as the default config file name. [email protected] supports both systems, while [email protected] only supports the new flat config.
+
+A guide on how to migrate to a flat config can be found [here](https://eslint.org/docs/latest/extend/plugin-migration-flat-config).
+
+The following official blog posts are available for interested parties:
+
+- https://eslint.org/blog/2022/08/new-config-system-part-1/
+- https://eslint.org/blog/2022/08/new-config-system-part-2/
+- https://eslint.org/blog/2022/08/new-config-system-part-3/
+
+This package contains a single flat config object which can be imported like so:
+
+```js
+const grafanaConfig = require("@grafana/eslint-config/flat");
+
+/**
+ * @type {Array<import('eslint').Linter.Config>}
+ */
+module.exports = [
+  {
+    grafanaConfig,
+  },
+];
+```
+
+You are then free to add/override properties.
+
+Note: Our shareable configs does not preconfigure `files`, `ignore`, or `languageOptions.globals`. For most of the cases, you probably want to configure some properties for your project.
+
+```js
+const grafanaConfig = require("@grafana/eslint-config/flat");
+
+/**
+ * @type {Array<import('eslint').Linter.Config>}
+ */
+module.exports = [
+  {
+    ignores: [".github", ".yarn", "**/build/", "**/compiled/", "**/dist/"],
+  },
+  grafanaConfig,
+  {
+    name: "myproject/defaults",
+    files: ["**/*.{ts,tsx,js,jsx}"],
+    rules: {
+      // add custom rules here.
+    },
+  },
+];
+```
+
 ## Publishing
 
 Publishing is handled by github actions which is triggered by a merge to master that contains a change to the version property in the `package.json` file. You can either do that manually or use the command below to version bump, commit and tag.