Added required directory %%WWWDIR%%/tmp/cache/tracker with correct permissions to pkg-plist.
Made the file %%WWWDIR%%/piwik.js writeable for user www, as systemChecks of matomo complains if that file is not writeable.

PR: 227364
Reviewed by: tz (mentor)
Approved by: tz (maintainer, mentor)
Differential Revision: https://reviews.freebsd.org/D15013