Add missing curl and coreutils in pulsarbot docker image (#4)

*Motivation*

`curl` and `base64` are required for running pulsarbot
diff --git a/pulsarbot/Dockerfile b/pulsarbot/Dockerfile
index 936ea5c..3e59202 100644
--- a/pulsarbot/Dockerfile
+++ b/pulsarbot/Dockerfile
@@ -9,7 +9,7 @@
 LABEL "com.github.actions.icon"="git-commit"
 LABEL "com.github.actions.color"="gray-dark"
 
-RUN apk add --update git jq bash && rm -rf /var/cache/apk/*
+RUN apk add --update git jq bash curl coreutils && rm -rf /var/cache/apk/*
 
 COPY entrypoint.sh /entrypoint.sh
 ENTRYPOINT ["/entrypoint.sh"]
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