example: document git_host in the config

fixes #20

example/config.jsonc

@@ -43,5 +43,8 @@
     // If enabled, all requests to the proxy will create their own thread.
     // this can increase the throughput of the proxy, especially when there are a lot of requests made
     // all at once.
-    "async_proxy": true
+    "async_proxy": true,
+
+    // If enabled, specific requests that look like git HTTP(s) clones will be let through.
+    "git_host": false
 }