doc/common/extensions: Fix classlink.

Allow the link to be different from the name.

This lets us fix the link for the Inventor Hub, which was linking to a non-existent page.

doc/common/extensions/classlink.py

@@ -5,13 +5,15 @@ from docutils.parsers.rst import Directive
 class PybricksClasslinkDirective(Directive):
 
     required_arguments = 1
+    optional_arguments = 1
 
     def run(self):
-        # Get link name from sphinx-directive
+        # Get link and name from sphinx-directive
         name = self.arguments[0]
+        link = name if len(self.arguments) == 1 else self.arguments[1]
 
         html = (
-            '<a href="{0}.html">'.format(name.lower()) +
+            '<a href="{0}.html">'.format(link.lower()) +
             '<dl class="py class">' +
             '<dt>' +
             '<em class="property">class </em>' +

doc/main/hubs/index.rst

@@ -38,7 +38,7 @@
     :height: 10 em
     :target: primehub.html
 
-.. pybricks-classlink:: InventorHub
+.. pybricks-classlink:: InventorHub PrimeHub
 
 .. figure:: ../../main/images/inventorhub.png
     :height: 10 em