Update dependabot.yml

Author: fhlavac

.github/dependabot.yml

@@ -7,6 +7,7 @@ updates:
       day: thursday
       time: "12:00"
       timezone: EST
+    workflow_dispatch:  # allow manual triggering
     versioning-strategy: increase
     allow:
       - dependency-type: "all"
@@ -27,6 +28,7 @@ updates:
       day: tuesday
       time: "12:00"
       timezone: EST
+    workflow_dispatch:  # allow manual triggering
     versioning-strategy: increase
     allow:
       - dependency-type: "all"