Add v3 to dependabot

Author: jessehouwing

.github/dependabot.yml

@@ -12,6 +12,10 @@ updates:
     directory: "/vsts-variable-set/v2"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "npm"
+    directory: "/vsts-variable-set/v3"
+    schedule:
+      interval: "weekly"
   - package-ecosystem: "npm"
     directory: "/vsts-variable-transform/v1"
     schedule:
@@ -20,3 +24,7 @@ updates:
     directory: "/vsts-variable-transform/v2"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "npm"
+    directory: "/vsts-variable-transform/v3"
+    schedule:
+      interval: "weekly"