docs: Added a simple contract to the README, and added a link to AgorApp courses

[frol]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• Commit messages follow the conventional commits spec
• If this is a code change: I have written unit tests.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

First-time developers need some catchy preview to get hooked. Without an example, and broken links to docs, we miss the opportunities.

Test Plan

n/a

Related issues/PRs

n/a

[frol]

@race-of-sloths include me

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@frol Thank you for your contribution! Your pull request is now a part of the Race of Sloths!

Current status: executed

Reviewer	Score
@race-of-sloths	1

Your contribution is much appreciated with a final score of 1!
You have received 25 (10 base + 15 weekly bonus) Sloth points for this contribution

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