Updates dependabot to scan all projects and Dockerfile (#1066)

Author: waldekmastykarz

.github/dependabot.yml

@@ -1,9 +1,14 @@
 version: 2
 updates:
 - package-ecosystem: nuget
-  directory: "/dev-proxy"
+  directories:
+    - "/dev-proxy"
+    - "/dev-proxy-abstractions"
+    - "/dev-proxy-plugins"
   schedule:
     interval: daily
-  open-pull-requests-limit: 5
-  labels:
-    - proxy
+
+- package-ecosystem: "docker"
+  directory: "/"
+  schedule:
+    interval: daily