README: add a short good-first-issues contributor on-ramp

[tsouth89]

Context

The README jumps from the Development section straight to Lineage/License. There is no pointer telling a newcomer where to start contributing, even though the repo has a good first issue label and a CONTRIBUTING.md.

Task

Add a small "Contributing" blurb to the README (a few lines, right after Development) linking to:

• the good first issue label,
• CONTRIBUTING.md,
• and the CLI reference doc once it exists (docs/CLI.md).

Acceptance criteria

• Concise (a short paragraph or a few bullets), matching the README's existing tone.
• All links resolve.
• No other README content changed.

How to test

Docs only — verify the rendered links on the PR preview.

Pointers

• README.md — insert after the Development section.

[Vermitrude]

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