Matomo support added to Celix website

[Roy Lenferink <rl...@apache.org>]

Hi folks,

Several Apache projects started using Matomo some time ago.
Matomo is a privacy friendly tool hosted on ASF hardware for tracking users
across a specified website.
I requested a snippet for Celix and added the snippet to the website.
This is useful to detect which pages our users are interested in so we can
focus on keeping the quality of those pages high (or improve the quality of
the less visited pages; depends how we want to read the statistics :-) ).

Since no user information is stored the website statistics are publicly
available via https://analytics.apache.org/

It might take some time before actual data is shown there, but using the
real-time log I could already see my visit appear.

Regards,
Roy