ci: add docker image

A docker image will be uploaded to github's registry on new
releases, it is also built as part of the QA job to ensure no
regressions.

.dockerignore

@@ -0,0 +1,10 @@
+docs/
+dist/
+.github/
+
+.dockerignore
+.gitignore
+
+Makefile
+README.md
+LICENSE

.github/workflows/qa.yaml

@@ -26,3 +26,11 @@ jobs:
         run: sqlc vet
       - name: Diff
         run: sqlc diff
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: false

Dockerfile

@@ -0,0 +1,14 @@
+FROM golang:1.22
+
+WORKDIR /app
+
+COPY . .
+
+ENV CGO_ENABLED=0
+RUN go build -o /bin/eryth ./cmd
+
+FROM scratch
+
+COPY --from=0 /bin/eryth /bin/eryth
+
+ENTRYPOINT ["eryth"]