Add dependabot configuration.

.github/dependabot.yml

@@ -0,0 +1,77 @@
+version: 2
+updates:
+- package-ecosystem: "github-actions"
+  directory: "/"
+  target-branch: trunk
+  schedule:
+    interval: "monthly"
+    time: "07:00"
+    timezone: "EST5EDT"
+  pull-request-branch-name:
+    separator: "-"
+  open-pull-requests-limit: 2
+  reviewers:
+  - joaander
+  groups:
+    actions-version:
+      applies-to: version-updates
+      patterns:
+      - '*'
+    actions-security:
+      applies-to: security-updates
+      patterns:
+      - '*'
+- package-ecosystem: "pip"
+  directory: "/"
+  target-branch: trunk
+  schedule:
+    interval: "monthly"
+    time: "07:00"
+    timezone: "EST5EDT"
+  pull-request-branch-name:
+    separator: "-"
+  open-pull-requests-limit: 2
+  reviewers:
+  - joaander
+  groups:
+    pip-version:
+      applies-to: version-updates
+      patterns:
+      - '*'
+      update-types:
+      - minor
+      - patch
+    pip-security:
+      applies-to: security-updates
+      patterns:
+      - '*'
+      update-types:
+      - minor
+      - patch
+- package-ecosystem: "cargo"
+  directory: "/"
+  target-branch: trunk
+  schedule:
+    interval: "monthly"
+    time: "07:00"
+    timezone: "EST5EDT"
+  pull-request-branch-name:
+    separator: "-"
+  open-pull-requests-limit: 2
+  reviewers:
+  - joaander
+  groups:
+    pip-version:
+      applies-to: version-updates
+      patterns:
+      - '*'
+      update-types:
+      - minor
+      - patch
+    pip-security:
+      applies-to: security-updates
+      patterns:
+      - '*'
+      update-types:
+      - minor
+      - patch

DESIGN.md

@@ -294,7 +294,6 @@ status may take a long time, so it should display a progress bar.
   without applying the additional submission filters.
 - **workspace**: The location on the file system that contains **directories**.
 
-# TODO: Dependabot configuration
 # TODO: readthedocs builds
 # TODO: logo
 # TODO: release CI