Documentation: Introduces a check stage to validate HTML and links

script/docs-verify-docker-image/Dockerfile

@@ -0,0 +1,20 @@
+FROM alpine:3.7
+
+RUN apk --no-cache --no-progress add \
+    ca-certificates \
+    curl \
+    findutils \
+    ruby-bigdecimal \
+    ruby-ffi \
+    ruby-json \
+    ruby-nokogiri \
+    tini \
+  && gem install --no-document html-proofer
+
+COPY ./validate.sh /validate.sh
+
+WORKDIR /app
+VOLUME ["/tmp","/app"]
+
+ENTRYPOINT ["/sbin/tini","-g","sh"]
+CMD ["/validate.sh"]