Add temporary link to developer wiki

There will be a finite period of time during the transfer from the wiki to
the hugo site where the wiki may still be more navigatable. So as to avoid
the documentation being inaccessable, provide a link to the wiki on the
hugo site header (that can be removed easily when the wiki is fully
decommissioned).

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

config.toml

@@ -28,18 +28,18 @@ languageCode = "en-us"
 # Menu
 [menu]
   # Header
+  [[menu.main]]
+    url = "http://wiki.apertis.org"
+    name = "Developer Wiki"
+    weight = 1
   [[menu.main]]
     url = "apertis_code_of_conduct/"
     name = "Code of Conduct"
-    weight = 1
+    weight = 2
   [[menu.main]]
     url = "https://gitlab.apertis.org"
     name = "GitLab"
-    weight = 2
-#  [[menu.main]]
-#    url = "/contact/"
-#    name = "contact"
-#    weight = 3
+    weight = 3
 
 # Links format
 #[permalinks]