Add dependency tests

- add `testGraphviz`: request `version` as AsciiArt and search for
  "Installation seems OK. File generation OK"
- irgnore `testGraphviz` inside github workflow tests except for the
  docker container tests, since only in the docker container case
  graphviz is available
- add `testMonacoEditorWebJar`: request `loader.js` and check if the
  server answers with status code 200
- add a note inside the pom where the webjar versions are hard coded
  inside the project

pom.xml

@@ -62,6 +62,13 @@
     <plantuml.version>1.2023.7</plantuml.version>
     <!-- Please keep the jetty version identical with the docker image -->
     <jetty.version>11.0.15</jetty.version>
+    <!--
+      While changing the version, please update the versions in the following files as well:
+      - src/main/webapp/components/app-head.jsp (script import)
+      - src/main/webapp/components/editor/editor.js : loadMonacoCodeEditorAsync (require.config)
+      - src/test/java/net/sourceforge/plantuml/servlet/TestDependencies.java : testMonacoEditorWebJar (JUnit Test)
+      as well as inside the pom.jdk8.xml :D
+    -->
     <monaco-editor.version>0.36.1</monaco-editor.version>
 
     <!-- dependencies -->