feat: add setup script for zettelkasten

.bin/setup-zk

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+if [ ! -d ~/.zk ]; then
+    echo "[zk] Setting up zettelkasten"
+    gh repo clone zk ~/.zk
+else
+    echo "[zk] Zettelkasten already set up. Use 'zk' to open it"
+fi