Fix docker issue adding --frozen

--frozen prevents Gemfile.lock from being updated,
which was causing write errors for me.

Also renames the image to lsm-hpce/docs

Dockerfile

@@ -3,7 +3,7 @@ FROM jekyll/builder
 WORKDIR /tmp
 ADD Gemfile /tmp/
 ADD Gemfile.lock /tmp/
-RUN bundle install
+RUN bundle install --frozen
 
 FROM jekyll/jekyll
 

docker-compose.yml

@@ -4,7 +4,7 @@ services:
     build:
       context: .
       dockerfile: Dockerfile
-    image: result/latest
+    image: lsm-hpce/docs
     ports:
       - "4001:4001"
     volumes: