Update README.md

Author: UrkoLekuona

README.md

@@ -4,13 +4,25 @@ Start writing posts quickly with docker
 ```
 git clone https://github.com/wearearima/wearearima.github.io.git
 $ cd wearearima.github.io
-$ docker run -p 4000:4000 --rm --volume="$PWD:/srv/jekyll" --volume="$PWD/vendor/bundle:/usr/local/bundle" -it jekyll/jekyll jekyll server
+$ docker run -p 4000:4000 --rm --volume="$PWD:/srv/jekyll" -it jekyll/jekyll jekyll server
 ```
 
 To see content in __draft_ folder
 ```
 $ git clone https://github.com/wearearima/wearearima.github.io.git
 $ cd wearearima.github.io
-$ docker run -p 4000:4000 --rm --volume="$PWD:/srv/jekyll" --volume="$PWD/vendor/bundle:/usr/local/bundle" -it jekyll/jekyll jekyll server --draft
+$ docker run -p 4000:4000 --rm --volume="$PWD:/srv/jekyll" -it jekyll/jekyll jekyll server --draft
 ```
-You can then access blog here: http://localhost:4000
+You can then access blog here: http://localhost:4000
+
+## Using cache
+
+In case you want to speed up consecutive builds, you can use Docker volumes to store Jekyll's gems locally. This can be done in like this:
+
+Create a docker volume:
+```
+docker volume create jekyll-ruby-gems
+```
+Each time we want to launch our Jekyll container, run it like this:
+````
+docker run --rm -p 4000:4000 --name jekyll --volume="$PWD:/srv/jekyll" --mount source=jekyll-ruby-gems,target=/usr/local/bundle -it jekyll/jekyll:3.8 jekyll serve