[TASK] Add method getBase to SiteInterface

Resolves: #86226
Releases: master
Change-Id: Idcffc65e6e040ab4f09e352f268aa4919c2abc59
Reviewed-on: https://review.typo3.org/58250


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>