Add 'Build your own Redis' under Ruby

[rohitpaulk]

Description

Added a 4-part tutorial series to build a toy Redis implementation in Ruby.

Motivation and Context

This tutorial covers the following topics:

• TCP servers
• the Redis protocol
• event loops

How Has This Been Tested?

Previewed markdown locally, tested all links.

Types of changes

• Content Update (change which fixes an issue or updates an already existing submission)
• New Article (change which adds functionality)
• Documentation change

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have made checks to ensure URLs and other resources are valid

[ThrashAbaddon]

Looks good.

[rohitpaulk]

Thanks @tuvtran!