ci: add Dependabot for monthly Go dependency updates

The creack/pty dependency should be kept up to date for security
and compatibility. Dependabot will open PRs automatically.

Co-Authored-By: Warp <agent@warp.dev>

Author: croaky

.github/dependabot.yml

@@ -0,0 +1,10 @@
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuring-dependabot-version-updates
+version: 2
+
+updates:
+  # Go
+  - package-ecosystem: gomod
+    directory: "/"
+    schedule:
+      interval: monthly
+    open-pull-requests-limit: 5