Use relative path to documentation images folder for GitHub

doc/org.eclipse.cdt.doc.user/README.md

@@ -0,0 +1,13 @@
+# C/C++ Development User Guide
+
+## AsciiDoc content
+
+The Asciidoctor Maven Plugin is configured to generate an HTML file in the `html/` folder for each AsciiDoc source file (`*.adoc`) placed in the `src/asciidoc/` folder.
+
+All AsciiDoc source files should include GitHub rendering support, as illustrated in the [example document](src/asciidoc/example.adoc).
+
+During content development, HTML files may be generated by invoking Maven locally:
+
+```
+mvn --define jgit.dirtyWorkingTree-cdtDefault=ignore --projects org.eclipse.cdt:org.eclipse.cdt.doc.user generate-resources
+```

doc/org.eclipse.cdt.doc.user/src/asciidoc/example.adoc

@@ -13,7 +13,7 @@ Contributors:
 
 // support image rendering and table of contents within GitHub
 ifdef::env-github[]
-:imagesdir: https://raw.githubusercontent.com/eclipse-cdt/cdt/main/doc/org.eclipse.cdt.doc.user/images
+:imagesdir: ../../images
 :toc:
 :toc-placement!:
 endif::[]