[FeatureRequest] Blueprint: allow mediapicker to be bound to folder #3909

Description

As an editor usting the grav-plugin-admin I would like to upload hero images and store them in a specified, common folder, so I can re-use the same image on another page.

Here, I want to choose exclusively from images in the common folder for quick selection.
This is currently possible only with type: filepicker, which gives a dropdown with very small previews.

Instead I would like to preview the images moderately large, as presented in type: mediapicker, so I can easily identify each image.

Acceptance criteria

• Blueprint fields of type: mediapicker exclusively retrieve images from folder: 'image://foo', if folder is specified

Further reading

• Compare issue [FeatureRequest] central media storage #3775
• Compare grav-plugin-admin issue #1696 Bad usability adding and selecting media #1696

Screenshot

• Currently type: mediapicker always retrieves images from "All Pages"