feat: mark experimental features as such

Author: innocenzi

src/Web/Documentation/content/main/1-essentials/05-database.md

@@ -1,7 +1,14 @@
 ---
 title: Database
+keywords: "Experimental"
 ---
 
+:::warning
+The ORM implementation of Tempest is currently experimental. Although you can use it, please note that it is not covered by our backwards compatibility promise.
+:::
+
+## Overview
+
 In contrast to many popular ORMs, Tempest models aren't required to be tied to the database. A model's persisted data can be loaded from any kind of data source: an external API, JSON, Redis, XML, … In essence, a model is nothing more than a class with public typed properties and methods. Tempest will use a model class' type information to determine how data should be mapped between objects.
 
 In other words, a model can be as simple as this class:

src/Web/Documentation/content/main/2-tempest-in-depth/03-auth.md

@@ -1,7 +1,14 @@
 ---
 title: Authentication and authorization
+keywords: "Experimental"
 ---
 
+## Overview
+
+:::warning
+The authentication and authorization implementations of Tempest are currently experimental. Although you can use them, please note that they are not covered by our backwards compatibility promise.
+:::
+
 Logging in (authentication )and verifying whether a user is allowed to perform a specific action (authorization) are two crucial parts of any web application. Tempest comes with a built-in authenticator and authorizer, as well as a base `User` and `Permission` model (if you want to).
 
 ## Authentication

src/Web/Documentation/content/main/2-tempest-in-depth/08-commands.md

@@ -1,5 +1,6 @@
 ---
 title: Command bus
+keywords: "Experimental"
 ---
 
 Tempest comes with a built-in command bus, which can be used to dispatch a command to its handler (synchronous or asynchronous). A command bus offers multiple advantages over a more direct approach to modelling processes: commands and their handlers can easily be tested in isolation, they are simple to serialize, and similar to the eventbus, the command bus also supports middleware.
@@ -78,6 +79,10 @@ final readonly class UserController()
 
 ## Async commands
 
+:::warning
+The asynchronous commands implementation of Tempest is currently experimental. Although you can use it, please note that it is not covered by our backwards compatibility promise.
+:::
+
 A common use case for Tempest's command bus is to dispatch asynchronous commands: commands that are executed by their handler in the background, outside the main PHP process. Making a command asynchronous is done by adding the `#[AsyncCommand]` to your command object:
 
 ```php