docs: Reactive Forms disable/enable functions are not part of the Reactive Forms guide

[geromegrignon]

Describe the problem that you experienced

Disabling a field is a common task.
However by using Reactive Forms you cannot longer rely on disabled attribute to disable a field: https://stackblitz.com/edit/stackblitz-starters-e5vfle

This issue does not question it.
But the only mention to enable/disable functions is in the Strictly typed reactive forms guide, as a link (https://stackblitz.com/edit/stackblitz-starters-e5vfle). Even here, that's just a link to the API reference, without proper explanation about the related functions to look at.

Enter the URL of the topic with the problem

https://angular.io/guide/reactive-forms

Describe what you were looking for in the documentation

enable/disable functions should be explained.

Describe the actions that led you to experience the problem

No response

Describe what you want to experience that would fix the problem

The Reactive Forms guide (https://angular.io/guide/reactive-forms) should include a section about enabling/disabling fields.

Add a screenshot if that helps illustrate the problem

No response

If this problem caused an exception or error, please paste it here

No response

If the problem is browser-specific, please specify the device, OS, browser, and version

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Provide any additional information here in as much as detail as you can

No response