add AUR publish support

packaging/aur/README.md

@@ -0,0 +1,21 @@
+# AUR publishing
+
+This repository includes an automated AUR publish workflow:
+- package files: `packaging/aur/dcr/PKGBUILD`, `packaging/aur/dcr/.SRCINFO`
+- workflow: `.github/workflows/aur.yml`
+
+## One-time setup
+
+1. Create the `dcr` package on AUR and initialize its git repository.
+2. Create an SSH key pair for CI.
+3. Add the public key to your AUR account.
+4. Add the private key to GitHub Actions secret `AUR_SSH_PRIVATE_KEY`.
+
+## Release flow
+
+1. Bump project version in `Cargo.toml`.
+2. Push tag `v<version>` (example: `v0.2.2`).
+3. GitHub Actions will:
+- compute source tarball SHA256
+- render `PKGBUILD` and `.SRCINFO`
+- push updates to `ssh://aur@aur.archlinux.org/dcr.git`