Update README.md

README.md

@@ -92,7 +92,7 @@ A sample post is available at `/1970-01-01-sample_post`. View it in the website
 You need `docker`:
 
 ```bash
-docker run --rm --volume="$PWD:/srv/jekyll" -p 4000:4000 -it jekyll/jekyll jekyll serve
+docker run --rm --volume="$PWD:/srv/jekyll" -p 4000:4000 -it jekyll/jekyll jekyll serve --incremental
 ```
 
 Site preview will be available at [localhost:4000](http://localhost:4000).
@@ -101,6 +101,8 @@ Site preview will be available at [localhost:4000](http://localhost:4000).
 
 **Note:** images from old posts will not display as they're not included in the repository.
 
+**Note:** you have to init submodule
+
 ## Preview on GitLab Pages
 
 1. Make sure you're working on a fork