[MINOR][SQL][STREAMING][DOCS] Fix minor typos, punctuations and grammar

## What changes were proposed in this pull request?

Minor fixes correcting some typos, punctuations, grammar.
Adding more anchors for easy navigation.
Fixing minor issues with code snippets.

## How was this patch tested?

`jekyll serve`

Author: Ahmed Mahran <ahmed.mahran@mashin.io>

Closes #14234 from ahmed-mahran/b-struct-streaming-docs.