Add common certs in trusted store of default docker image

.dockerignore

@@ -0,0 +1,2 @@
+Dockerfile
+contrib/docker

contrib/docker/Dockerfile

@@ -8,7 +8,7 @@ RUN cargo build --release
 
 FROM debian:$TARGET-slim
 
-RUN apt-get update && apt-get install -y openssl && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y openssl ca-certificates && rm -rf /var/lib/apt/lists/*
 COPY --from=builder /code/target/release/acmed /usr/local/bin/acmed
 COPY --from=builder /code/target/release/tacd  /usr/local/bin/tacd
 CMD ["/usr/local/bin/acmed", "-f", "--log-stderr"]

contrib/docker/build-docker-image.sh

@@ -1,4 +1,8 @@
 #!/bin/bash
+# ACMED certificate watcher and renewer daemon.
+# Helper script to build debian based docker image
+# Author: Nicolas Karageuzian
+
 set -euo pipefail
 
 DIR="$( cd "$( dirname "$0" )/../.." >/dev/null 2>&1 && pwd )"