dependabot: add bundler package-ecosystem for docs (#1123)

Author: mmorel-35

.github/dependabot.yml

@@ -1,5 +1,13 @@
 version: 2
 updates:
+- package-ecosystem: "bundler"
+  directory: "/docs"
+  schedule:
+    interval: daily
+    time: '01:00'
+  open-pull-requests-limit: 5
+
+
 - package-ecosystem: gomod
   directory: "/"
   schedule:
@@ -13,4 +21,4 @@ updates:
   schedule:
     interval: daily
     time: '01:00'
-  open-pull-requests-limit: 5
+  open-pull-requests-limit: 5