feat(ci): move rust docker target bash to shell script

ci/rust-docker-target.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+
+set -e
+
+#tag=
+#branch=
+#push=
+
+build() {
+    bin=$1
+    extra=$2
+
+    f=$(mktemp)
+
+    cat > $f << EOF
+FROM alpine:latest
+COPY .docker-bin/$bin /bin/$bin
+$extra
+CMD ["/bin/$bin"]
+EOF
+
+    echo "building $dockerfile"
+
+    $dockerfile | docker build -t ghcr.io/pluralkit/$bin:$tag -f $f .
+
+    rm $f
+
+    if [ "$push" == "true" ]; then
+      docker push ghcr.io/pluralkit/$bin:$tag
+      docker image tag ghcr.io/pluralkit/$bin:$tag ghcr.io/pluralkit/$bin:$branch
+      docker push ghcr.io/pluralkit/$bin:$branch
+      if [ "$branch" == "main" ]; then
+        docker image tag ghcr.io/pluralkit/$bin:$tag ghcr.io/pluralkit/$bin:latest
+        docker push ghcr.io/pluralkit/$bin:latest
+      fi
+    fi
+}
+
+# add rust binaries here to build
+build api
+build gateway
+build avatars