[FEATURE] Allow .ts file extension for static typoscript templates

[FEATURE] Allow .ts file extension for static typoscript templates

Static TypoScript support alternative primary names for constants and
setup file:
* constants.ts
* setup.ts

Old names are still working:
* constants.txt
* setup.txt

Resolves: #34922
Releases: master
Change-Id: I6868c22c95337812e6946f16655f024f2ed80471
Reviewed-on: http://review.typo3.org/40264
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>