PLG-33 Sumo Logic Sample Data (Astronomy) app doc

[ishaanahuja29]

Purpose of this pull request

This pull request is to create apps doc for Sumo Logic Sample Data (Astronomy) app.
NOTE: Its not required for all customers, so I've not added it to sidebar/ product list. It'll be accessed via link directly.

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

PLG-33

[cla-bot]

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[ishaanahuja29]

The build-and-deploy step should pass once #4606 is merged as this PR is referring to a c2c source doc in that PR.

[jpipkin1]

This article looks very good, @ishaanahuja29. I had only a couple of minor suggestions about adding borders to images.