Add Webrick to the Docker image

docker/Dockerfile

@@ -4,13 +4,15 @@ LABEL maintainer="Sergey Fedorov <[email protected]>"
 LABEL repository="strech/sidekiq-prometheus-exporter"
 
 ENV RACK_VERSION 2.2.6.4
+ENV WEBRICK_VERSION 1.8.1
 ENV SIDEKIQ_VERSION 6.5.8
 ENV REDIS_NAMESPACE_VERSION 1.10
 ENV SIDEKIQ_PROMETHEUS_EXPORTER_VERSION 0.2.0
 
 RUN    addgroup -S exporter \
     && adduser -s /bin/false -SDHg exporter exporter \
     && gem install "rack:$RACK_VERSION" \
+    && gem install "webrick:$WEBRICK_VERSION" \
     && gem install "sidekiq:$SIDEKIQ_VERSION" \
     && gem install "redis-namespace:$REDIS_NAMESPACE_VERSION" \
     && gem install "sidekiq-prometheus-exporter:$SIDEKIQ_PROMETHEUS_EXPORTER_VERSION"

lib/sidekiq/prometheus/exporter/version.rb

@@ -6,7 +6,7 @@ module Exporter
       # NOTE: Every version update dropds Docker patch version to 0
       #       and every adjustment in Docker setup bumps it to +1
       VERSION = '0.2.0'.freeze
-      DOCKER_PATCH_VERSION = '0'.freeze
+      DOCKER_PATCH_VERSION = '1'.freeze
     end
   end
 end