Update README.md

Author: alex-titarenko

README.md

@@ -1,3 +1,8 @@
 ## About this repo
 
 This repo is used for hosting Linux releases of NotesHub.
+NotesHub is not open source software and this repo **DOES NOT** contain the source code of NotesHub.
+
+## Sponsorship
+If you like the project and would like to help, consider [sponsorship](https://github.com/sponsors/NotesHubApp).
+The development takes a lot of my valuable free time and monetary rewards would encourage me continue the development.