feat: initialize markr nostr bookmark client

- Add project structure with TypeScript, React, and Vite
- Implement nostr authentication using browser extension (NIP-07)
- Add NIP-51 compliant bookmark fetching and display
- Create minimal UI with login and bookmark components
- Integrate applesauce-core and applesauce-react libraries
- Add responsive styling with dark/light mode support
- Include comprehensive README with setup instructions

This is a minimal MVP for a nostr bookmark client that allows users to
view their bookmarks according to NIP-51 specification.

node_modules/nostr-tools/lib/esm/nip13.js

@@ -0,0 +1,52 @@
+// nip13.ts
+import { bytesToHex as bytesToHex2 } from "@noble/hashes/utils";
+import { sha256 } from "@noble/hashes/sha256";
+
+// utils.ts
+import { bytesToHex, hexToBytes } from "@noble/hashes/utils";
+var utf8Decoder = new TextDecoder("utf-8");
+var utf8Encoder = new TextEncoder();
+
+// nip13.ts
+function getPow(hex) {
+  let count = 0;
+  for (let i = 0; i < 64; i += 8) {
+    const nibble = parseInt(hex.substring(i, i + 8), 16);
+    if (nibble === 0) {
+      count += 32;
+    } else {
+      count += Math.clz32(nibble);
+      break;
+    }
+  }
+  return count;
+}
+function minePow(unsigned, difficulty) {
+  let count = 0;
+  const event = unsigned;
+  const tag = ["nonce", count.toString(), difficulty.toString()];
+  event.tags.push(tag);
+  while (true) {
+    const now = Math.floor(new Date().getTime() / 1e3);
+    if (now !== event.created_at) {
+      count = 0;
+      event.created_at = now;
+    }
+    tag[1] = (++count).toString();
+    event.id = fastEventHash(event);
+    if (getPow(event.id) >= difficulty) {
+      break;
+    }
+  }
+  return event;
+}
+function fastEventHash(evt) {
+  return bytesToHex2(
+    sha256(utf8Encoder.encode(JSON.stringify([0, evt.pubkey, evt.created_at, evt.kind, evt.tags, evt.content])))
+  );
+}
+export {
+  fastEventHash,
+  getPow,
+  minePow
+};