adding docker to dependabot

.github/dependabot.yml

@@ -11,3 +11,11 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
+
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      # Prefix all commit messages with "[docker] " (no colon, but a trailing whitespace)
+      prefix: "[docker] "

Dockerfile

@@ -1,5 +1,5 @@
 # sample dockerfile for testing call-docker-build.yaml
-FROM alpine:edge
+FROM alpine:3.17.1
 
 RUN apk add --no-cache curl