Use JS ESLint configs instead of JSON

This is to avoid ERR_IMPORT_ASSERTION_TYPE_MISSING on recent Node.js with updated ESLint.
Fixes errors like the following: ".eslintrc.es6.json" needs an import assertion of type "json"

[MAILPOET-5061]

packages/js/eslint-config/.eslintrc-premium.js

@@ -0,0 +1,34 @@
+module.exports = {
+  extends: ['airbnb', 'plugin:react/jsx-runtime', 'prettier'],
+  env: {
+    browser: true,
+  },
+  parser: '@babel/eslint-parser',
+  parserOptions: {
+    ecmaVersion: 6,
+    ecmaFeatures: {
+      jsx: true,
+    },
+  },
+  plugins: ['react-hooks'],
+  settings: {
+    'import/resolver': 'webpack',
+  },
+  rules: {
+    'class-methods-use-this': 0,
+    // React hooks rules
+    'react-hooks/rules-of-hooks': 'error',
+    'react-hooks/exhaustive-deps': 'warn',
+    'import/prefer-default-export': 0, // we want to stop using default exports and start using named exports
+    // Exceptions
+    'import/extensions': 0, // we wouldn't be able to import jQuery without this line
+    'jsx-a11y/anchor-is-valid': [
+      'error',
+      {
+        components: ['Link'],
+        specialLink: ['to'],
+      },
+    ],
+    'import/no-default-export': 1, // no default exports
+  },
+};