[FEATURE] Make the dimensions of feedit popup configurable

Use TsConfig to change the width & height of the popup used in the
edit panel of EXT:feedit.

Resolves: #18586
Releases: master
Change-Id: Ifbc7ebae75a3454fbfe9a70f0a2b4b1d95a2c094
Reviewed-on: https://review.typo3.org/48617


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>