Update ponyc image location to ghcr.io (#132)

.github/workflows/cargo-check.yaml

@@ -1,4 +1,4 @@
-name: cargo checks
+name: Cargo checks
 
 on:
   pull_request:

.github/workflows/docker-image-builds.yml

@@ -0,0 +1,16 @@
+name: Docker image builds
+
+on: pull_request
+
+concurrency:
+  group: pr-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  validate-docker-image-builds:
+    name: Validate Docker image builds
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Docker build
+        run: "docker build --pull docker/."

docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM ponylang/ponyc:release-alpine
+FROM ghcr.io/ponylang/ponyc:release-alpine
 COPY bin/compile.sh bin/evaluate.sh /usr/local/bin/
 
 ENV CC=gcc