Update README

README.md

 # Angel Guide for Chaos Events
 
+This guide is written in Asciidoc.
+
 ## Requirements
 * asciidoctor
 * asciidoctor-pdf
 
-## How to build the PDF
+## Asciidoctor resources
 
-We need to specify asset and fonts directories to build the guide properly.
+[Quick Reference](https://asciidoctor.org/docs/asciidoc-syntax-quick-reference/)
+[User Manual](https://asciidoctor.org/docs/user-manual/)
+
+## How to build the PDF
 
-e.g. for the camp2019
+Run the following command in the git repositories root folder, after installing
+the requirements.
 
 ```
-  $ asciidoctor-pdf -a pdf-theme=asset/camp2019/theme.yml -a pdf-fontsdir=asset/camp2019/fonts index.adoc
+  $ asciidoctor-pdf guide.adoc
 ```