Document that "hidden" files and folders are never included in a PCK

This closes https://github.com/godotengine/godot/issues/32826.

about/troubleshooting.rst

@@ -100,6 +100,10 @@ considered resources. For example, if you load ``test.json`` in the exported
 project, you need to specify ``*.json`` in the non-resource export filter. See
 :ref:`doc_exporting_projects_export_mode` for more information.
 
+Also, note that files and folders whose name begin with a period will never be
+included in the exported project. This is done to prevent version control
+folders like ``.git`` from being included in the exported PCK file.
+
 On Windows, this can also be due to :ref:`case sensitivity
 <doc_project_organization_case_sensitivity>` issues. If you reference a resource
 in your script with a different case than on the filesystem, loading will fail

getting_started/workflow/export/exporting_projects.rst

@@ -122,6 +122,12 @@ select every scene or resource you want to export.
 
 .. image:: img/expselected.png
 
+.. note::
+
+    Files and folders whose name begin with a period will never be included in
+    the exported project. This is done to prevent version control folders like
+    ``.git`` from being included in the exported PCK file.
+
 Exporting from the command line
 -------------------------------