feat: add Developer Skills Challenge section and CHALLENGE.md for mattpo

[gordonzhaomwrf-a11y]

在根目录下创建 CHALLENGE.md 文件，描述 Memanto + Matt Pocock 开发者技能挑战的详情、奖励与参与方式，并在 README.md 中添加链接和徽章。

Summary by CodeRabbit

• Documentation
  • Added Developer Skills Challenge documentation with requirements, bonus points, prizes, and participation instructions.
  • Updated README with challenge callout and badge for improved visibility.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR introduces a new Memanto + Matt Pocock Developer Skills Challenge by adding a comprehensive CHALLENGE.md specification file and updating the README to promote it with a badge, promotional section, and minor formatting fixes to the comparison table and license heading.

Changes

Developer Skills Challenge Documentation

Layer / File(s)	Summary
Challenge specification document CHALLENGE.md	Complete specification including core and bonus requirements, prize details, judging criteria, timeline, participation steps (Moorcheh API key signup and GitHub Issue submission), and terms/questions section.
README challenge promotion and formatting README.md	Adds challenge badge/link in the top banner, new promotional section with challenge description and link to full details, corrects comparison table formatting with separator row, and adjusts MIT License heading placement.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A challenge most grand, from Matt Pocock's hand,
Memory primitives, temporal strands,
Badges and badges, in README bright,
Moorcheh awaits developers' might!
✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately and specifically summarizes the main change: adding a Developer Skills Challenge section and CHALLENGE.md file, which aligns with the actual changes to both README.md and the new CHALLENGE.md file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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Warning

⚠️ This pull request might be slop. It has been flagged by CodeRabbit slop detection and should be reviewed carefully.

[coderabbitai]

🧹 Nitpick comments (1)

CHALLENGE.md (1)

42-42: ⚡ Quick win

Consider specifying an exact deadline date.

The deadline is currently "30 days from now" with a reference to Discord for the exact date. This adds friction for participants who need to check another platform. Consider either:

• Adding a specific date (e.g., "June 28, 2026")
• Computing it from the PR merge/announcement date
• Or keeping the Discord reference but making it clearer this is a soft timeline

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@CHALLENGE.md` at line 42, Update the "Submission deadline" row in
CHALLENGE.md to replace the vague "30 days from now (see exact date on Discord)"
with a clear deadline: either an explicit date (e.g., "June 28, 2026"), a
computed rule tied to the PR merge/announcement, or a clarified soft timeline
with Discord as secondary; locate the table row labeled "Submission deadline"
and modify that cell text accordingly so contributors can see the exact timeline
without needing Discord.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@CHALLENGE.md`:
- Line 42: Update the "Submission deadline" row in CHALLENGE.md to replace the
vague "30 days from now (see exact date on Discord)" with a clear deadline:
either an explicit date (e.g., "June 28, 2026"), a computed rule tied to the PR
merge/announcement, or a clarified soft timeline with Discord as secondary;
locate the table row labeled "Submission deadline" and modify that cell text
accordingly so contributors can see the exact timeline without needing Discord.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3db1f133-cd7e-48de-8991-4d7d0f68958b

📥 Commits

Reviewing files that changed from the base of the PR and between dd38ad3 and 6ee4bbf.

📒 Files selected for processing (2)

• CHALLENGE.md
• README.md