[TASK] Add more files to .gitignore

composer.lock and everything below typo3conf/ should be excluded if
the core checkout is used as document root directly.

Resolves: #61483
Releases: 6.3, 6.2
Change-Id: I34e706c510c38d953a98f0f30789f87fc968ae52
Reviewed-on: http://review.typo3.org/32691
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>