Fix missing images in editor preview due to wrong links (#31299) (#31393)

Backport #31299

Parse base path and tree path so that media links can be correctly
created with /media/.

Resolves #31294

---------

Co-authored-by: Brecht Van Lommel <brecht@blender.org>

modules/markup/renderer.go

@@ -84,10 +84,10 @@ type RenderContext struct {
 }
 
 type Links struct {
-	AbsolutePrefix bool
-	Base           string
-	BranchPath     string
-	TreePath       string
+	AbsolutePrefix bool   // add absolute URL prefix to auto-resolved links like "#issue", but not for pre-provided links and medias
+	Base           string // base prefix for pre-provided links and medias (images, videos)
+	BranchPath     string // actually it is the ref path, eg: "branch/features/feat-12", "tag/v1.0"
+	TreePath       string // the dir of the file, eg: "doc" if the file "doc/CHANGE.md" is being rendered
 }
 
 func (l *Links) Prefix() string {