chore: refine Docker setup and configuration

- Add a new `.hadolint.yaml` configuration file with specific rule ignores
- Update the Dockerfile to install `ca-certificates` without a fixed version

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.hadolint.yaml

@@ -0,0 +1,3 @@
+ignored:
+  - DL3018
+  - DL3008

docker/Dockerfile

@@ -12,7 +12,7 @@ LABEL org.opencontainers.image.source=https://github.com/appleboy/drone-discord
 LABEL org.opencontainers.image.description="Drone Discord"
 LABEL org.opencontainers.image.licenses=MIT
 
-RUN apk add --no-cache ca-certificates=20230506-r0 && \
+RUN apk add --no-cache ca-certificates && \
   rm -rf /var/cache/apk/*
 
 COPY release/${TARGETOS}/${TARGETARCH}/drone-discord /bin/