add documentation for global locals

Signed-off-by: ngn <[email protected]>

docs/app.md

@@ -107,3 +107,12 @@ to a 404 page, you set a custom route for this:
 ```c
 ctorm_app_all(app, all_route);
 ```
+
+### Global locals
+If you want to pass a variable to all the routes and middlewares, you can use global
+locals:
+```c
+ctorm_app_local(app, "config", &config);
+```
+To access the local from the route or the middleware handler, you can use `REQ_LOCAL` or
+`ctorm_req_local`. See the [request documentation](req.md) for more information.

docs/req.md

@@ -155,3 +155,5 @@ you can access the "username" local:
 char *username = REQ_LOCAL("username");
 // char *username = ctorm_req_local(req, "username", NULL);
 ```
+If you want to pass a variable to all routes/middlewares, you should use global locals. See
+the [app documentation](app.md).