* Docs: Adding a Markdown Style Guide

What this PR does / why we need it: This request builds a markdown style guide for writers documenting information about Grafana services for users.
This PR serves the need to make documentation and READMEs more consistent and maintainable.

Which issue(s) this PR fixes: This request fixes the issue grafana#19592

Fixes grafana#19592

Special notes for your reviewer:

@marcusolsson and @oddlittlebird, sorry for the delay. I've set up the style guide, and it is ready for review, or additional sections.

* Docs: Adding a Markdown Style Guide

What this PR does / why we need it: This request builds a markdown style guide for writers documenting information about Grafana services for users.
This PR serves the need to make documentation and READMEs more consistent and maintainable.

Which issue(s) this PR fixes: This request fixes the issue grafana#19592

Fixes grafana#19592

Special notes for your reviewer:

@marcusolsson and @oddlittlebird, sorry for the delay. I've set up the style guide, and it is ready for review, or additional sections.

* Docs: fixing typos and char repetition

Editing some typos in the text, and removing the repetition of A and B characters that appeared in the file.

* Docs: Changing content following review of new Markdown Style Guide

- adjustment to headings to sentence case.
- adding an introduction
- removing punctuation content
- making suggested word and punctuation fixes

Fixes #19592