docs(pdfexport): add Timeline to the ToC of the offline PDF docs

Author: pepinho24

_pdf.yml

@@ -119,6 +119,7 @@ intro_columns:
       "SearchBox": "searchbox/overview"
       "SiteMap": "sitemap/overview"
       "Tab Strip": "tabstrip/overview"
+      "Timeline": "timeline/overview"
       "ToggleButton": "togglebutton/overview"
       "ToolBar": "toolbar/overview"
       "TreeView": "treeview/overview"
@@ -158,4 +159,4 @@ intro_columns:
     items:
       "Compression": "controls/radcompression"
       "Script Manager": "scriptmanager/overview"
-      
+