chore: Update sponsor information

Author: GermanCoding

.github/FUNDING.yml

@@ -1 +1,2 @@
-custom: ['https://github.com/GermanCoding/synctrayzor/blob/main/DONATING.md#donating']
+custom: ['https://github.com/GermanCoding/synctrayzor/blob/main/DONATING.md#donating']
+github: GermanCoding

DONATING.md

@@ -14,4 +14,9 @@ While development is done for free by a fantastic team, running the infrastructu
 If you make use of these, I kindly ask that you consider sending a small amount towards funding Syncthing's running costs and future development.
 Donations are handled by the Syncthing Foundation, whose accounts are public.
 
-[Donate to Syncthing](https://syncthing.net/donations/).
+[Donate to Syncthing](https://syncthing.net/donations/).
+
+SyncTrayzor
+-----------
+
+If you wish to donate to me directly, I have a [GitHub sponsors page](https://github.com/sponsors/GermanCoding). Note that I am not directly involved with Syncthing development (nor do I receive funding from them), but only SyncTrayzor development.