Add renovate.json for centralized dependency management (#6)

Enable Renovate dependency updates by inheriting the shared config
from bootc-dev/infra. See docs/SOP-new-repository.md in that repo
for details.

Assisted-by: OpenCode (claude-opus-4-6)

Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

renovate.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>bootc-dev/infra:renovate-shared-config.json"
+  ]
+}