Updated FAQ (markdown)

FAQ.md

@@ -14,4 +14,19 @@ antigen boundle skywind3000/z.lua
 antigen boundle changyuheng/fz
 
 function _z() { _zlua "$@"; }
-```
+```
+
+## Use `z` as `cd`
+
+Paste this script in your `.bashrc` / `.zshrc`:
+```bash
+function j() {
+    if [[ "$argv[1]" == "-"* ]]; then
+        z "$@"
+    else
+        cd "$@" 2> /dev/null || z "$@"
+    fi
+}
+```
+
+When you are using `j xxx` it will first try `cd xxx` and then `z xxx` if cd failed.