[TASK] Streamline formatting of html templates

The indentations in the HTML templates are out of control.
Even if we provide an EditorConfig, which should ensure
that the files are all uniformly indented. There seems to
have been an increasing aversion to TABS over time.

This has led to the fact that above all newly created templates
have always been indented with SPACES instead of TABS.
We now have a mix of TABS and SPACES in our project, partly
also in a single file.

To avoid this in the future, all existing templates were converted
to indentations with SPACES and the provided EditorConfig was
adapted. In order to really, really make sure that it doesn't get
out of hand, we also introduce a new linter, which ensures
that all HTML templates are properly indented.

Resolves: #88180
Releases: master
Change-Id: I86d23120bc68e3696f398b1ae76f1efc4804d501
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60522


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Oliver Wand <wand@itaw.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>