Add new section to have a local HTTP server easily

Author: GuillaumeGomez

src/rustdoc-internals.md

@@ -192,3 +192,18 @@ runtime. These tests don't have as thorough of a writeup, but a broad example
 that features results in all tabs can be found in `basic.js`. The basic idea is
 that you match a given `QUERY` with a set of `EXPECTED` results, complete with
 the full item path of each item.
+
+## Testing locally
+
+Some features of the generated HTML documentation might require the local
+storage to be used across pages, which isn't working well without an HTTP
+server. To still be able to test these features locally, the best way is to
+simply run a local HTTP server, like this:
+
+```bash
+$ cd build/[YOUR ARCH]/doc
+$ python3 -m http.server
+```
+
+Now you can browse your documentation just like you would if it was hosted
+on the internet. To get the `std` page index, the URL will be "/std/index.html".