Update readme.md

The fingerprint hash is alphanumeric but the nginx regex tests for a numeric string.

readme.md

@@ -108,7 +108,7 @@ RewriteRule ^(.+)\.([0-9a-z]{32})\.(js|css)$ $1.$3 [L]
 
 **Nginx virtual host setup**
 ```
-location ~ (.+)\.(?:\d+)\.(js|css)$ {
+location ~ (.+)\.(?:\w+)\.(js|css)$ {
     try_files $uri $1.$2;
 }
 ```