Optional arguments for field type "media" are missing

[LordRazen]

Description for Enhancement

Since I updated my field types due to this issue (https://github.com/vdm-io/Joomla-Component-Builder/issues/788) a minute ago, I recognized two optional attributes are missing for the field type "media".

I work with very small images, so the default size of 200px height stretches the images a lot...

Enhancement:

Add the missing parameters to the Field Type "media" / the field type updater:

Properties:
preview_width
preview_height

Adjustable: true
Mandatory: false
Translateable: false
Value: 200

Description:
(optional) sets the max-width of preview image (default: "200").
(optional) sets the max-height of preview image (default: "200").

Here's the official Joomla Info:
https://docs.joomla.org/Media_form_field_type

[Llewellynvdm]

This is the repo where we manage these changes.

@TLWebdesign we should in a next update also change these. Lets do one change per pull request, and not mix them up.