devel-docs: Add a urlmap file

The urlmap file allows gi-docgen to generate links for namespaces that
are also generated by gi-docgen. For example, with this commit, a
reference to `GObject` will now be properly linked to the GObject
documentation.

devel-docs/reference/gimp-ui/gimp-ui-3.0.toml.in

@@ -106,3 +106,4 @@ content_images = [
   'images/string-combo-box.png',
   'images/unit-combo-box.png',
 ]
+urlmap_file = "urlmap.js"

devel-docs/reference/gimp-ui/urlmap.js

@@ -0,0 +1,9 @@
+// A map between namespaces and base URLs for their online gi-docgen documentation
+baseURLs = [
+  [ 'GLib', 'https://docs.gtk.org/glib/' ],
+  [ 'GObject', 'https://docs.gtk.org/gobject/' ],
+  [ 'Gdk', 'https://docs.gtk.org/gdk3/' ],
+  [ 'GdkPixbuf', 'https://docs.gtk.org/gdk-pixbuf/' ],
+  [ 'Gio', 'https://docs.gtk.org/gio/' ],
+  [ 'Gtk', 'https://docs.gtk.org/gtk3/' ],
+]

devel-docs/reference/gimp/gimp-3.0.toml.in

@@ -72,3 +72,4 @@ base_url = "https://gitlab.gnome.org/GNOME/gimp/-/blob/master/"
 [extra]
 content_files = [
 ]
+urlmap_file = "urlmap.js"

devel-docs/reference/gimp/urlmap.js

@@ -0,0 +1,9 @@
+// A map between namespaces and base URLs for their online gi-docgen documentation
+baseURLs = [
+  [ 'GLib', 'https://docs.gtk.org/glib/' ],
+  [ 'GObject', 'https://docs.gtk.org/gobject/' ],
+  [ 'Gdk', 'https://docs.gtk.org/gdk3/' ],
+  [ 'GdkPixbuf', 'https://docs.gtk.org/gdk-pixbuf/' ],
+  [ 'Gio', 'https://docs.gtk.org/gio/' ],
+  [ 'Gtk', 'https://docs.gtk.org/gtk3/' ],
+]