Add FUNDING

My current funding is non-profit and will be delegated to other upstream projects I use. So I think it would be reasonable to add. I can also add more active contributors later or even `testcontainers` itself.

P.S: I raised it on the `#contributors` Testcontainers Slack, no response from the team. So I guess that's fine :)

.github/FUNDING.yml

@@ -0,0 +1 @@
+github:oleg-nenashev