feat: add security headers for GitHub Pages

Author: christophernemala

docs/tutorialkit.dev/public/_headers

@@ -0,0 +1,13 @@
+/*
+  Cross-Origin-Embedder-Policy: require-corp
+  Cross-Origin-Opener-Policy: same-origin
+  X-Content-Type-Options: nosniff
+  X-Frame-Options: DENY
+  X-XSS-Protection: 1; mode=block
+  Referrer-Policy: strict-origin-when-cross-origin
+
+/_astro/*
+  Cache-Control: public, max-age=31536000, immutable
+
+/assets/*
+  Cache-Control: public, max-age=31536000, immutable