style: remove eslint with frontend code removal ADR

- Add ADR for frontend code removal
- Drop eslint, as explained in the ADR

cms/static/js/features_jsx/.eslintrc.js

@@ -1,14 +0,0 @@
-module.exports = {
-    extends: '@edx/eslint-config',
-    root: true,
-    settings: {
-        'import/resolver': 'webpack',
-    },
-    rules: {
-        indent: ['error', 4],
-        'react/jsx-indent': ['error', 4],
-        'react/jsx-indent-props': ['error', 4],
-        'import/extensions': 'off',
-        'import/no-unresolved': 'off',
-    },
-};