feat: add support for sysctls compose key (#239)

* feat: add support for `sysctls` compose key

* lint

---------

Co-authored-by: Pasha Sviderski <me@psviderski.name>

pkg/client/compose/testdata/compose-full-spec.yaml

@@ -23,6 +23,8 @@ services:
     privileged: true
     pull_policy: always
     scale: 3
+    sysctls:
+      - net.ipv4.ip_forward=1
     user: nginx:nginx
     volumes:
       - /etc/passwd:/host/etc/passwd:ro