Add Dependabot to auto-update go-sdk dependency (#458)

Configure Dependabot to monitor github.com/optimizely/go-sdk/v2 releases
and automatically create PRs when new versions are available.

- Checks weekly on Mondays
- Only watches go-sdk dependency (ignores other deps)
- Auto-assigns fullstack-sdk-maintainers for review
- Labels PRs with "dependencies" and "go-sdk"

This eliminates manual go.mod updates when go-sdk releases new versions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: Mat001

.github/dependabot.yml

@@ -0,0 +1,19 @@
+version: 2
+updates:
+  # Monitor go-sdk releases and auto-create PRs
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    # Only watch the go-sdk dependency
+    allow:
+      - dependency-name: "github.com/optimizely/go-sdk/v2"
+    commit-message:
+      prefix: "deps"
+    labels:
+      - "dependencies"
+      - "go-sdk"
+    reviewers:
+      - "optimizely/fullstack-devs"
+    open-pull-requests-limit: 5