chore(eslint): lint examples/bunyan and prepare for linting .js and .mjs files

This adds support for 'npm run lint' in examples/bunyan, using the same
base eslint.config.js used by most of the repo.

There are ulterior motives:
- This is a first step to linting all the examples using the same
  base config (rather than the spotty linting of examples using the
  separate "examples/.eslintrc".
- The eslint.config.js changes support being used to lint .ts,
  .js, and .mjs files reasonably. I'll follow-up with a separate PR
  adding linting of .mjs files used for some ESM testing
  (e.g. "instrumentation-ioredis/test/fixtures/use-ioredis.mjs")

Hattip to the following for some of the eslint config changes:
  https://github.com/open-telemetry/opentelemetry-js/pull/4446/files#diff-1a88e8e72db982c999acf146817a416a02d93547458e6525610cf69b24751af9

Author: trentm

eslint.config.js

@@ -5,10 +5,10 @@ module.exports = {
     "node",
     "prettier"
   ],
-  extends: ["eslint:recommended", "plugin:@typescript-eslint/recommended", "plugin:prettier/recommended"],
+  extends: ["eslint:recommended", "plugin:prettier/recommended"],
   parser: "@typescript-eslint/parser",
   parserOptions: {
-    "project": "./tsconfig.json"
+    "project": null
   },
   rules: {
     "quotes": ["error", "single", { "avoidEscape": true }],
@@ -28,6 +28,11 @@ module.exports = {
   overrides: [
     {
       files: ['*.ts'],
+      // Enable typescript-eslint for ts files.
+      extends: ["eslint:recommended", "plugin:@typescript-eslint/recommended", "plugin:prettier/recommended"],
+      parserOptions: {
+        "project": "./tsconfig.json"
+      },
       rules: {
         "@typescript-eslint/no-floating-promises": "error",
         "@typescript-eslint/no-this-alias": "off",
@@ -49,21 +54,39 @@ module.exports = {
           }
         }],
         "@typescript-eslint/no-shadow": ["warn"],
+        "prefer-rest-params": "off",
       }
     },
     {
       files: ["test/**/*.ts"],
+      // Enable typescript-eslint for ts files.
+      extends: ["eslint:recommended", "plugin:@typescript-eslint/recommended", "plugin:prettier/recommended"],
+      parserOptions: {
+        "project": "./tsconfig.json"
+      },
       rules: {
         "no-empty": "off",
         "@typescript-eslint/ban-ts-ignore": "off",
+        "@typescript-eslint/ban-types": ["warn", {
+          "types": {
+            "Function": null,
+          }
+        }],
         "@typescript-eslint/no-empty-function": "off",
         "@typescript-eslint/no-explicit-any": "off",
         "@typescript-eslint/no-unused-vars": "off",
         "@typescript-eslint/no-var-requires": "off",
         "@typescript-eslint/no-shadow": ["off"],
         "@typescript-eslint/no-floating-promises": ["off"],
         "@typescript-eslint/no-non-null-assertion": ["off"],
-        "@typescript-eslint/explicit-module-boundary-types": ["off"]
+        "@typescript-eslint/explicit-module-boundary-types": ["off"],
+        "prefer-rest-params": "off",
+      }
+    },
+    {
+      files: ["*.mjs"],
+      parserOptions: {
+        sourceType: 'module',
       }
     }
   ]

examples/bunyan/.eslintrc.js

@@ -0,0 +1,26 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+
+const baseConfig = require('../../eslint.config');
+
+module.exports = {
+  ...baseConfig,
+  env: {
+    node: true,
+  },
+};

examples/bunyan/package.json

@@ -4,6 +4,8 @@
   "version": "0.1.0",
   "description": "Example of Bunyan integration with OpenTelemetry",
   "scripts": {
+    "lint": "eslint . --ext=ts,js,mjs",
+    "lint:fix": "eslint . --ext=ts,js,mjs --fix",
     "start": "node -r ./telemetry.js app.js"
   },
   "repository": {