Missing critical detail about @preact/signals-react when following installation guide for React

[jfreyheit]

@preact/signals v2 requires to add "import "@preact/signals/auto";" at top-level (this is done in Modular form's playground for React, which uses @preact/signals-react v2.2).

However, when following the installation guide, @preact/signals v2 is installed but there's no mention of the need to add this line of code. As a result, signals don't work properly.

We should either install @preact/signals v1 explicitly (through npm install @preact/signals-react@1"), or mention the required extra code.

[fabian-hiller]

We use import "@preact/signals/auto"; as a quick fix in our playground. If I understand correctly, it is usually recommended to use Preact's Bable plugin instead.