Enhance policy system with global rules and age validation

- Updated policy configuration to include global rules applicable to all events, allowing for site-wide security policies.
- Introduced age validation features to prevent replay and clock skew attacks, with configurable maximum age limits for events.
- Enhanced example policy and README documentation to reflect new global rules and age validation capabilities.
- Added comprehensive tests for global rule checks and age validation scenarios.
- Bumped version to v0.16.2.

.gitignore

@@ -96,6 +96,8 @@ cmd/benchmark/data
 !*.tsx
 !bun.lock
 !*.svelte
+!.github/**
+!.github/workflows/**
 # ...even if they are in subdirectories
 !*/
 /blocklist.json