Add npm run lint to CI and to docs

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

support/guides/development/styleguide.md

@@ -4,7 +4,7 @@
 
 We format our code with the Elixir Formatter and check for issues with [Credo](https://github.com/rrrene/credo) (a few rules are not blocking).
 
-Please run those two commands before pushing code :
+Please run those two commands before pushing code:
  * `mix format`
  * `mix credo`
  
@@ -15,4 +15,8 @@ These two commands must not return an error code, since they are required to pas
 We use `tslint` with the `tslint-config-airbnb` preset.
 Errors should be reported when running in dev mode `npm run dev` or when building a production bundle `npm run build`.
 
+Please run the following command before pushing code `npm run lint`.
+
+This command must not return an error code, since it's required to pass inside CI.
+
 We also try to follow the [official Vue.js style guide](https://vuejs.org/v2/style-guide/).