Improving eslint and tsconfig files to avoid errors (#328)

These changes fix the error that is present in all the `.ts` files of the background package.

packages/background/.eslintrc.js

@@ -0,0 +1,25 @@
+module.exports = {
+    env: {
+        browser: true,
+        es2021: true,
+    },
+    extends: [
+        'eslint:recommended',
+        'plugin:@typescript-eslint/recommended',
+        'prettier',
+    ],
+    parser: '@typescript-eslint/parser',
+    parserOptions: {
+        ecmaVersion: 12,
+        sourceType: 'module',
+        project: 'tsconfig.json',
+        tsconfigRootDir: __dirname,
+    },
+    plugins: ['@typescript-eslint'],
+    ignorePatterns: ['**/*.js', 'test/'],
+    rules: {
+        '@typescript-eslint/no-empty-interface': ['warn'],
+        '@typescript-eslint/await-thenable': ['warn'],
+        '@typescript-eslint/no-explicit-any': 'off',
+    },
+};

packages/background/tsconfig.json

@@ -27,6 +27,7 @@
         "experimentalDecorators": true
     },
     "include": ["src", "test"],
+    "exclude": [".eslintrc.js", "test/mocks/sinonChrome.js"],
     "ts-node": {
         "files": true
     }