add Asciidoctor & Plantuml to Contributing guide

README.adoc

@@ -40,7 +40,7 @@ Once you've cloned the project repo, you can run your own local Hugo server via
  sh serve.sh
 ----
 
- NOTE: You will also need Graphviz (2.38.0 recommended) and https://plantuml.com/download[Plantuml] installed in order to be able to render UML diagrams.
+NOTE: You will also need https://graphviz.org/[Graphviz] (2.38.0 recommended) and https://plantuml.com/download[Plantuml] installed in order to be able to render UML diagrams.
 
 === Option 2: Using Docker (Recommended for Windows users)
 

content/en/docs/How-To Guides/Contribution guidelines/_index.adoc

@@ -13,17 +13,17 @@ These guidelines assume that you're familiar with the GitHub workflow.
 
 == How to Contribute
 
-We use https://gohugo.io/[Hugo] to format and generate our website, the
-https://github.com/google/docsy[Docsy] theme for styling and site structure,
+We use https://gohugo.io/[Hugo] and https://asciidoctor.org/[ Asciidoctor] to format and generate our website,
+the https://github.com/google/docsy[Docsy] theme for styling and site structure,
+https://graphviz.org/[Graphviz] and https://plantuml.com/[plantuml] for rendering diagrams,
 and https://github.com/peaceiris/actions-gh-pages[GitHub Actions for GitHub Pages] to manage the deployment of the site.
 Hugo is an open-source static site generator that provides us with templates,
-content organisation in a standard directory structure, and a website generation
-engine. You write the pages in Markdown (or HTML if you want), and Hugo wraps them up into a website.
+content organisation in a standard directory structure, and a website generation engine.
+You write the pages in Markdown (or HTML if you want), and Hugo wraps them up into a website.
 
-All submissions, including submissions by project members, require review. We
-use GitHub pull requests for this purpose. Consult
-https://help.github.com/articles/about-pull-requests/[GitHub Help] for more
-information on using pull requests.
+All submissions, including submissions by project members, require review.
+We use GitHub pull requests for this purpose.
+Consult https://help.github.com/articles/about-pull-requests/[GitHub Help] for more information on using pull requests.
 
 == How to write good documentation