chore(docs): mention data sources for feature and module tables

Author: jspanchu

docs/roadmap/features.md

@@ -6,6 +6,8 @@
 > [!NOTE]
 > Detailed information about each feature will be added soon.
 
+Contribute to this data here: [features.json](https://github.com/Kitware/vtk-wasm/blob/main/docs/roadmap/features.json)
+
 <script setup>
 import roadMapData from './features.json';
 </script>

docs/roadmap/modules.md

@@ -1,7 +1,10 @@
 # Module Availability
 
-This table categorizes VTK modules based on their availability in the JavaScript API, indicating whether they are automatically marshaled, manually marshaled, or ignored for some reason.
+This table categorizes VTK modules based on their availability in the JavaScript API, indicating whether the classes are marshalled, or ignored for some reason.
 
-Use search and status filters to quickly find module availability.
+The data is sourced from the VTK GitHub repository, where the status of each module is tracked in three categories: [auto-marshalled](https://github.com/Kitware/VTK/blob/master/Utilities/Marshalling/VTK_MARSHALAUTO.txt), [ignored](https://github.com/Kitware/VTK/blob/master/Utilities/Marshalling/ignore.txt), and [manually marshalled](https://github.com/Kitware/VTK/blob/master/Utilities/Marshalling/VTK_MARSHALMANUAL.txt).
+
+> [!TIP]
+> Use search and status filters to quickly find module availability.
 
 <ModulesCoverageTable />