fix(Dockerfile): jekyll install

Dockerfile

@@ -1,15 +1,12 @@
-FROM jruby:9.2.18.0-jdk11 as build-image
+FROM jekyll/jekyll:4.2.0 as build-image
 
-RUN apt-get update \
-    && apt-get upgrade -y \
-    && apt-get install -y build-essential npm \
-    && apt-get install -y iputils-ping \
-    && apt-get autoremove --purge -y \
-    && apt-get clean -y \
-    && rm -rf /var/lib/apt/lists/*
-
-
-RUN gem install jekyll
+RUN apk update \
+    && apt-get upgrade \
+    && apt-get add --no-cache \
+        build-base
+        gcc \
+        npm \
+        iputils
 
 RUN npm install -g fsh-sushi
 
@@ -35,4 +32,4 @@ RUN chmod +x /app/docker-entrypoint.sh
 
 COPY --from=build-image /build /app
 
-ENTRYPOINT ["/app/docker-entrypoint.sh"]
+ENTRYPOINT ["/app/docker-entrypoint.sh"]