feat: add section for key metrics guide

[FatumaA]

Description

This PR adds a key metrics guide section to the documentation.

Related Tickets & Documents

Fixes #407

Mobile & Desktop Screenshots/Recordings

N/A

Steps to QA

1. Run the project locally
2. Notice the new sidebar entry under the "Getting Started" section.
3. See that all the mentioned metrics are covered.

Tier (staff will fill in)

• Tier 1
• Tier 2
• Tier 3
• Tier 4

[optional] What gif best describes this PR or how it makes you feel?

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[BekahHW]

This is really great, Fatuma. There are a couple of comments in the review.

We might want to add YOLO Coders as well. Here's more info on that: https://opensauced.pizza/blog/yolo-coder.

[FatumaA]

This is really great, Fatuma. There are a couple of comments in the review.

We might want to add YOLO Coders as well. Here's more info on that: https://opensauced.pizza/blog/yolo-coder.

Thank you. I've made the requested changes.

[BekahHW]

It's almost there! Reading through it again, I think it makes more sense to use the third person instead of second person. We also want to make sure that the sections are written for a general audience (including teams, maintainers, and contributors) and not just contributors.

[FatumaA]

so want to make sure that the sections are written for a general audience (including teams, maintainers, and contributors) and not just contributors.

Makes sense! Done 🙂