docs: add merchandise support page

Add a merchandise page to the docs navigation and position it around a shared Open Collective funding path instead of direct shirt sales. Clarify that shirts are a manual thank-you perk rather than an automatic purchase flow.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: shenxianpeng

docs/merch.md

@@ -0,0 +1,85 @@
+# Support cpp-linter with a T-shirt
+
+cpp-linter is **not** opening a general T-shirt store right now.
+
+Instead, we want one shared project fund so support goes to the project as a whole, not to only one maintainer. That makes it much easier to cover printing, shipping, and the occasional T-shirt thank-you gift fairly.
+
+## Why a shared fund comes first
+
+If supporters donate to individual maintainers separately, it creates an awkward problem: one person may receive the money while someone else is expected to handle the shirt, inventory, or shipping.
+
+Our preferred model is:
+
+1. Support goes into one public project account.
+2. The core maintainers manage it together.
+3. Shirt fulfillment is offered manually when budget, stock, and shipping make sense.
+
+This keeps expectations clear and avoids turning project support into private side payments.
+
+## Shared funding path
+
+!!! tip "Preferred setup"
+    Support cpp-linter through our shared Open Collective account: [opencollective.com/cpp-linter](https://opencollective.com/cpp-linter)
+
+[Support cpp-linter on Open Collective](https://opencollective.com/cpp-linter){ .md-button .md-button--primary }
+
+Why Open Collective:
+
+- It gives the project a shared public account instead of sending funds to only one person.
+- It makes incoming funds and project expenses easier to track transparently.
+- It gives the maintainers a cleaner way to share responsibility for project spending.
+
+We may still add GitHub Sponsors later, but this Open Collective page is now the **canonical shared destination** for project support.
+
+## What supporters should expect
+
+!!! important "No active checkout yet"
+    There is no public order form or direct purchase flow at the moment.
+
+If you want to support cpp-linter, the intended model is:
+
+- Donate through [Open Collective](https://opencollective.com/cpp-linter).
+- If we are offering shirts at that time, we will confirm availability manually.
+- A shirt is a **thank-you perk**, not an automatic purchase entitlement.
+
+That means fulfillment may depend on:
+
+- available stock
+- shipping destination
+- sizing availability
+- current project budget
+
+## T-shirt policy
+
+We still like the idea of project shirts, but only in a lightweight and sustainable way.
+
+Our working policy is:
+
+1. The shirt is meant to thank notable supporters of the project.
+2. We will confirm each shipment manually before collecting size and address details.
+3. We will avoid promising fulfillment unless the shared fund can cover it.
+4. Limited quantity, international shipping, and cost changes may affect availability.
+
+## If you want one
+
+The shared fund is live, and the best starting point is:
+
+- [Open Collective for cpp-linter](https://opencollective.com/cpp-linter)
+
+If you specifically want to express interest in a shirt, the best follow-up channels are:
+
+- [GitHub Discussions](https://github.com/cpp-linter/cpp-linter/discussions)
+- [Issues in this site repository](https://github.com/cpp-linter/cpp-linter.github.io/issues)
+
+If enough people are interested, we can publish a clearer supporter policy around shirt availability and supporter tiers.
+
+## Next steps
+
+The remaining rollout is:
+
+1. Add this same support link to the main repository.
+2. Publish the maintainer policy for how project funds are used.
+3. Define when a supporter may be offered a shirt.
+4. Add GitHub Sponsors later only if it still points people back to the shared funding model.
+
+Thanks for supporting cpp-linter and helping us keep the project fair for everyone involved.

mkdocs.yml

@@ -9,6 +9,7 @@ nav:
   - Home: index.md
   - Getting Started: getting-started.md
   - Discussion: discussion.md
+  - Merchandise: merch.md
   # - Blog:
   #     - blog/index.md
 exclude_docs: |