feat: add report input to generate a maturity report

[shenxianpeng]

What

Adds a report input. When set to true, the action generates a human-readable DevOps maturity report and writes it to the GitHub Actions job summary, so it renders right on the workflow run page.

- uses: devops-maturity/devops-maturity-action@v1
  with:
    github-token: ${{ secrets.GITHUB_TOKEN }}
    report: true

The report includes the overall score & level, a per-category breakdown (with a little bar), the met criteria, and the unmet ones with their improvement recommendations.

How

• New report input, default 'false' — fully backward compatible; existing workflows are unaffected.
• The assessment step already runs dm config --format json; it now also persists that JSON to $RUNNER_TEMP. A new optional step (if: inputs.report == 'true') reads it and builds the Markdown from the CLI's existing fields (score, level, category_scores, passed, failed) — no extra CLI invocation, no new dependency.
• New report-path output points at a Markdown copy of the report, written to $RUNNER_TEMP (outside the repo, so it's never committed to the badge PR) for optional artifact upload.
• README: documented the input/output and added a Reports section with examples (job summary + upload-artifact).

Example output

# DevOps Maturity Report — devops-maturity

**Score:** 79.3%  ·  **Level:** SILVER

## Category breakdown
| Category | Score | |
|---|---:|:--|
| Basics | 100% | `██████████` |
| Quality | 57% | `██████░░░░` |
| Supply Chain Security | 86% | `█████████░` |
...

## Improvement recommendations (2)
- **D405 · SBOM Generation** — Generate an SBOM for each release.
- **D202 · Functional Testing**

Validation

• action.yml passes the repo's CI check (yaml.safe_load + required keys + composite).
• The embedded report script py_compiles cleanly and was smoke-tested against a representative dm config --format json payload (output shown above).

🤖 Generated with Claude Code

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Generated by Claude Code