Update dependency eslint to v9 (#52)

* Update dependency eslint to v9

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/node.js.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [18.x]
+        node-version: [20.x]
     steps:
     - uses: actions/checkout@v4
     - name: Use Node.js ${{ matrix.node-version }}

.github/workflows/npm-publish.yml

@@ -10,21 +10,27 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [20.x]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 16
+          node-version: ${{ matrix.node-version }}
       - run: npm ci
 
   publish-npm:
     needs: build
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [20.x]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 16
+          node-version: ${{ matrix.node-version }}
           registry-url: https://registry.npmjs.org/
       - run: npm ci
       - run: npm run lint

eslint.config.mjs

@@ -0,0 +1,46 @@
+import prettier from "eslint-plugin-prettier";
+import globals from "globals";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import js from "@eslint/js";
+import { FlatCompat } from "@eslint/eslintrc";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    recommendedConfig: js.configs.recommended,
+    allConfig: js.configs.all
+});
+
+export default [...compat.extends("eslint:recommended", "prettier"), {
+    plugins: {
+        prettier,
+    },
+
+    languageOptions: {
+        globals: {
+            ...globals.browser,
+            ...globals.commonjs,
+        },
+
+        ecmaVersion: "latest",
+        sourceType: "script",
+    },
+
+    rules: {
+        indent: ["error", 2],
+        "linebreak-style": ["error", "unix"],
+        quotes: ["error", "double"],
+        semi: ["error", "always"],
+        "prettier/prettier": "error",
+    },
+}, {
+    files: ["**/*.test.js"],
+
+    languageOptions: {
+        globals: {
+            ...globals.jest,
+        },
+    },
+}];