feat: add description for multiple toggle

[vsgoulart]

Closes #1391

• This PR adds a new form-js element or visually changes an existing component.
  • => In that case, we need to ensure we follow up on this, e.g. by creating an issue in Tasklist

[vsgoulart]

@volodymyr-melnykc I made some small changes in the text, you can check it here

[volodymyr-melnykc]

@vsgoulart Thanks for the update. Having a message under the switcher looks good!

When the switcher is off, the message says "The picker variable will return an array with single" missing the wording "file" at the end. Can we update it to "The picker variable will return an array with a single file"?

Also, I noticed strange behavior with the switcher. Sometimes it doesn't change the state when clicking on it, or automatically switches even when not clicking on it. Here's a video recording:

file.picker.switcher.mov