docs: add a contributing guide and link it from the README and site

Nothing in the repo said that pull requests go to develop rather than master,
or that release-plz reads the commit subject to pick the next version. Both
cost a first-time contributor a round trip.

CONTRIBUTING.md covers those, the three checks CI runs, and the fact that the
e2e suites skip without a soulfind server. The README and the community page
link to it, and it joins the footer's Project column.

CONTRIBUTING.md

@@ -0,0 +1,43 @@
+# Contributing
+
+Issues and pull requests are both welcome, and so is just saying what's missing.
+No contributor agreement, no template.
+
+## Pull requests
+
+Branch off `develop` and target `develop`. `master` only moves through a release
+PR.
+
+Write the subject as a
+[conventional commit](https://www.conventionalcommits.org), like
+`fix(lib): route on the full four-byte message code`. release-plz reads these to
+pick the next version and write the changelog. One change per pull request;
+small ones land fastest.
+
+Before you push:
+
+```bash
+cargo fmt --all
+cargo clippy --workspace --all-targets --all-features -- -D warnings
+cargo test
+```
+
+CI runs those on Linux, macOS and Windows, plus an end-to-end suite against a
+real [soulfind](https://github.com/soulfind-dev/soulfind) server. The e2e suites
+skip when no server is around, so `cargo test` stays green without one.
+[Development](./README.md#development) has the setup if you want to run them.
+
+AI-assisted changes are fine, and no need to say so. Keep the trailers out of
+the commit message: no `Co-Authored-By:` for a model, no session links.
+
+## Issues
+
+The command you ran, what you expected, and what happened is plenty.
+`RUST_LOG=trace` output helps. Don't worry about polishing it.
+
+Built something on `soulseek-rs-lib`? Open a PR adding it to the README, and
+reserve a client minor version in
+[#12](https://github.com/michel/soulseek-rs/issues/12) so it's identifiable on
+the network.
+
+Contributions are under MIT, like the rest of the project.

README.md

@@ -647,6 +647,12 @@ soulfind instead of skipping.
   points `SOULFIND_BIN` at it, and runs both the library and CLI e2e suites
   with `SOULSEEK_E2E_REQUIRED=1`, so a missing server fails instead of skipping.
 
+## Contributing
+
+Issues and pull requests both welcome. Branch off `develop`, keep the change
+small, and see [CONTRIBUTING.md](./CONTRIBUTING.md) for the commit convention
+and the checks CI runs.
+
 ## License
 
 MIT. See [LICENSE](./LICENSE).

website/src/components/layout/footer.tsx

@@ -20,6 +20,7 @@ const COLUMNS: readonly FooterColumn[] = [
     links: [
       { label: "GitHub", href: LINKS.gh },
       { label: "Issues", href: LINKS.issues },
+      { label: "Contributing", href: LINKS.contributing },
       { label: "Releases", href: LINKS.releases },
       { label: "Changelog", href: LINKS.changelog },
     ],

website/src/lib/links.ts

@@ -3,6 +3,7 @@ export const LINKS = {
   issues: 'https://github.com/michel/soulseek-rs/issues',
   releases: 'https://github.com/michel/soulseek-rs/releases',
   changelog: 'https://github.com/michel/soulseek-rs/blob/master/CHANGELOG.md',
+  contributing: 'https://github.com/michel/soulseek-rs/blob/master/CONTRIBUTING.md',
   license: 'https://github.com/michel/soulseek-rs/blob/master/LICENSE',
   cratesClient: 'https://crates.io/crates/soulseek-rs',
   cratesLib: 'https://crates.io/crates/soulseek-rs-lib',

website/src/pages/community.tsx

@@ -239,10 +239,15 @@ export const Community = () => {
               open-source Soulseek server; run it locally to develop against a real protocol
               implementation without touching the public network.
             </p>
+            <p>
+              Pull requests go to <Code>develop</Code>; <Code>master</Code> only moves on a
+              release.
+            </p>
             <div className="mt-1 flex flex-wrap gap-2 sm:gap-3">
               <Button href={LINKS.issues} variant="accent">
                 Open an issue
               </Button>
+              <Button href={LINKS.contributing}>Contributing</Button>
               <Button href={LINKS.gh}>GitHub</Button>
             </div>
           </Prose>