doc: Add an aux section to changelog config

doc/changes/.proclamation.json

@@ -12,6 +12,9 @@
         "Drivers": {
             "directory": "drivers"
         },
+        "Helper Libraries": {
+            "directory": "aux"
+        },
         "Misc. Features": {
             "directory": "misc_features"
         },

doc/changes/aux/.gitignore

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: CC0-1.0
+# SPDX-FileCopyrightText: 2020 Collabora, Ltd. and the Proclamation contributors
+!.gitignore