Add a proportionate code of conduct

Not the Contributor Covenant — that document is written for projects with
contributors and a review process, and this repo accepts no pull requests.
There is an issue surface now, so a short standard for it is real rather than
ceremony: be civil, one issue per problem, no pitches, no personal data.

Author: RelayStack

CODE_OF_CONDUCT.md

@@ -0,0 +1,32 @@
+# Code of conduct
+
+This repository publishes the source of a commercial website and accepts **issue
+reports** about it. That is the whole community here, and the standard is short.
+
+## In issues
+
+- Be civil. Critique the work, not the person.
+- One issue per problem, with a URL or a file path.
+- Accessibility and broken-link reports are always welcome, however small.
+- No advertising, no link-dropping, no "I can build this for you" pitches.
+- No disclosure of anyone's personal data, including your own.
+
+## Not here
+
+- **Work enquiries** belong on [Telegram](https://t.me/relaystack).
+- **Security reports** must not be public. See [SECURITY.md](SECURITY.md).
+- **Pull requests** for the site's copy, design or pricing are not accepted. See
+  [CONTRIBUTING.md](CONTRIBUTING.md).
+
+## Enforcement
+
+I moderate this repository alone. Anything that breaks the two lines above gets
+closed, and repeat behaviour gets blocked. There is no appeals committee — that is
+what a one-person business looks like — so the standard is deliberately kept to
+things most people already do.
+
+## Attribution
+
+Deliberately not the Contributor Covenant. That document is written for projects
+with maintainers, contributors and a review process. Borrowing it here would be
+costume.