[ BUG ] Examples / docs with sequential write without a callback are not ideal

[huntharo]

Describe the bug

• The examples where we write to a sitemap or index with .write('item') repeated, are not correct / not ideal
• These write calls do not respect backpressure because they do not wait for the callback to be called before writing another item

Expected behavior

We can change these to use a promisified version of write to show how to make multiple writes while respecting back pressure and handling errors as they happen

Context:

• Library Version 7.1.1

Additional context

None