[BUGFIX] Allow sysfolder as subpages in vhs menu helpers

In https://github.com/FluidTYPO3/vhs/commit/8d989b05b2bcdfe4ffa54d4855133887aec200fe the behavior was introduced to ignore sysfolders in general. This PR doesnt change this default behavior. The user can however modify ``excludeSubpageTypes`` to not include sysfolder and that way, with this PR, sysfolders will be included as subpages