Configure dependabot for 1.4.x branch

Closes gh-1909

Author: sjohnr

.github/dependabot.yml

@@ -23,6 +23,22 @@ updates:
         update-types:
           - version-update:semver-major
           - version-update:semver-minor
+  - package-ecosystem: gradle
+    target-branch: 1.4.x
+    directory: /
+    schedule:
+      interval: daily
+      time: '03:00'
+      timezone: Etc/UTC
+    labels:
+      - 'type: dependency-upgrade'
+    registries:
+      - spring-milestones
+    ignore:
+      - dependency-name: '*'
+        update-types:
+          - version-update:semver-major
+          - version-update:semver-minor
   - package-ecosystem: gradle
     target-branch: main
     directory: /
@@ -48,6 +64,13 @@ updates:
       interval: weekly
     labels:
       - 'type: task'
+  - package-ecosystem: github-actions
+    target-branch: 1.4.x
+    directory: /
+    schedule:
+      interval: weekly
+    labels:
+      - 'type: task'
   - package-ecosystem: github-actions
     target-branch: main
     directory: /
@@ -71,6 +94,13 @@ updates:
       interval: weekly
     labels:
       - 'type: task'
+  - package-ecosystem: npm
+    target-branch: 1.4.x
+    directory: /docs
+    schedule:
+      interval: weekly
+    labels:
+      - 'type: task'
   - package-ecosystem: npm
     target-branch: main
     directory: /docs