[REF] tools: rename extras into tools

doc/tooling.md

@@ -1,5 +1,16 @@
 # 🦉 Tooling 🦉
 
+
+To help work/improve/learn with OWL, we have here:
+
+- a benchmarks application
+- a playground application
+
+Both of them can be accessed by using a static http server.  A simple python
+server is available in `server.py`.  There is also a npm script to start it:
+`npm run extras` (and its version with a watcher: `npm run extras:watch`).
+
+
 ## Development mode
 
 By default, Owl is in *production* mode, this means that it will try to do its
@@ -15,4 +26,15 @@ owl.__info__.mode = 'dev';
 ```
 
 Note that templates compiled with the `prod` settings will not be recompiled.
-So, changing this setting is best done at startup.
+So, changing this setting is best done at startup.
+
+## Benchmarks
+
+The benchmarks application is a very small application, implemented in different
+frameworks, and in different versions of Owl.  This is a simple internal tool,
+useful to compare various performance metrics on some tasks.
+
+## Playground
+
+The playground is an important application designed to help learning and
+experimenting with Owl.  It is available [online](https://odoo.github.io/owl/playground/).