[FEATURE] Provide integration for powermail

[lukaszuznanski]

Add extension with fluid templates to properly render powermail output. This should be published on https://github.com/TYPO3-Initiatives/headless_powermail @lukaszuznanski will publish the POC and then the issue can be tuned an polished by somebody else.

[lukaszuznanski]

solved by creating headless_powermail extension