cache, vendor and silverstripe-cache entries are actually patterns

and not prefixes, as I assumed based on the old entry for
silverstripe-cache.
Now they are the same as in .htaccess

Also add statements for using silverstripe's 500 error page.
404 entry is not enabled, since in the example it only applies to
assets, any "real" URL is handled by the php (that in turn then returns
the 404 page when there is no matching page in the database), and there
is little sense to send a nicely designed page to the browser that
doesn't even care.