Building idb library

1. Install Rollup
2. Download the appropriate source code from https://github.com/jakearchibald/idb/releases
3. Extract the archive and navigate to the source root
4. Replace the contents of rollup.config.js with

const iffeIttr = {
  input: './with-async-ittr.js',
  output: {
    file: 'build/iife/with-async-ittr.js',
    format: 'iife',
    name: 'idb'
  },
};

export default [
  iffeIttr,
];

5. Execute rollup -c in the console
6. The built library can be found in build/iife/