Add Dockerfile to Renovate includePaths (#71)

Dockerfile was not being scanned by Renovate because it was not
included in the includePaths allowlist. This adds the Dockerfile*
pattern to enable automatic dependency updates for Docker images.

Author: mensfeld

renovate.json

@@ -8,7 +8,8 @@
     ".ruby-version",
     "Gemfile",
     "llm-docs-builder.gemspec",
-    ".github/workflows/**"
+    ".github/workflows/**",
+    "Dockerfile*"
   ],
   "ignorePaths": [
     "spec/integrations"