docs: add the Zcash provider to the README (JUMEMB-113)

[chybisov]

Which Linear task is linked to this PR?

JUMEMB-113 — documentation follow-up to #884, which added @lifi/widget-provider-zcash.

Why was it implemented this way?

The README listed every provider package except the new one:

• Install: a "Zcash (destination only)" block with pnpm, npm and yarn, like the other providers.
• Architecture: an entry for @lifi/widget-provider-zcash — it validates t1/t3 and Orchard u1 receivers, needs no wallet and no extra install, and without it the widget offers no ZEC.
• Multi-chain example: ZcashProvider() after BitcoinProvider().
• Widget Light: one sentence that Zcash is not available there yet (widget-embedded does not register ZcashProvider()).
• CLAUDE.md: the overview now names Stellar, which it had left out, and Zcash as a destination-only chain.

Docs only, so no changeset. The public-docs pages follow in a separate PR in lifinance/public-docs.

Visual showcase (Screenshots or Videos)

Not applicable: README text only.

Checklist before requesting a review

• I have performed a self-review and testing of my code.
• This pull request is focused and addresses a single problem.
• If this PR modifies the Widget API or adds new features that require documentation, I have updated the documentation in the public-docs repository. — In a separate lifinance/public-docs PR.

[changeset-bot]

⚠️ No Changeset found

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