chore: add Dockerfile and basic CI test

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+---
+name: CI
+on: [push]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+        with:
+          go-version: 1.18
+      - name: Install dependencies
+        run: go mod download
+      - name: Build binary
+        run: make
+      - name: Run and make request
+        run: |
+          ./bin/dotkatapult --port=8080 &
+          curl --silent --retry 10 --retry-delay 1 --retry-connrefused \
+              http://localhost:8080/