ci: consider workspace directories for package-lock updates

according to dependabot/dependabot-core#6270, this is the solution

Author: johannes-vogel

.github/dependabot.yml

@@ -3,7 +3,7 @@ version: 2
 updates:
 - package-ecosystem: npm
   directory: /
-  versioning-strategy: increase-if-necessary
+  versioning-strategy: increase
   schedule:
     interval: weekly
   groups:
@@ -20,4 +20,4 @@ updates:
       versions: ["8.x"]
     - dependency-name: "express"
         # express 5 not supported atm
-      versions: ["5.x"]
+      versions: ["5.x"]