docs: improve example code

[is2ei]

Updated examples in README.

• Made the first example consistent with the second example. The second example uses Hello as example string and has comment.
• Removed duplicated code in the third example.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm