cmd/ht: check in autogenerated documentation for checks
cmd/ht: check in autogenerated documentation for checks

Technically this is nonsens: The documentation is autogenerated with
list-checks.bash.
But: This list of check provides valuable information, e.g. while
working through the Tutorial.md, so let's put it online.

vdobler/ht,vdobler/ht,vdobler/ht,vdobler/ht