Add static Matomo integration to theme

** Why are these changes being introduced:

* We want to receive web traffic reports about users to our digital
  exhibits platforms, and have defined a site profile within Matomo for
  this purpose.

** Relevant ticket(s):

* https://mitlibraries.atlassian.net/browse/post-36

** How does this address that need:

* This creates a separate javascript file in the theme, matomo.js, which
  has the needed JS calls to our Matomo instance. I'm hard-coding the
  property ID within this partial because there is no need for different
  sites to use different profiles.

** Document any side effects to this change:

* This approach means that changes to our Matomo setup will require code
  changes to the theme, and also - as far as this change goes - means
  that sites which don't use our theme will not be included in our
  analytics. Ultimately this integration should probably be handled at
  the module level, but for now we've just got a theme to deal with.

Author: matt-bernhardt

asset/js/matomo.js

@@ -0,0 +1,11 @@
+var _paq = window._paq = window._paq || [];
+/* tracker methods like 'setCustomDimension' should be called before 'trackPageView' */
+_paq.push(['trackPageView']);
+_paq.push(['enableLinkTracking']);
+(function() {
+  var u='https://matomo.libraries.mit.edu/';
+  _paq.push(['setTrackerUrl', u+'matomo.php']);
+  _paq.push(['setSiteId', '9']);
+  var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
+  g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s);
+})();

view/layout/layout.phtml

@@ -26,6 +26,7 @@ $this->headScript()->prependFile($this->assetUrl('vendor/jquery/jquery.min.js',
 $this->headScript()->appendFile($this->assetUrl('js/global.js', 'Omeka'));
 $this->headScript()->appendFile($this->assetUrl('js/smartmenus/dist/jquery.smartmenus.min.js'));
 $this->headScript()->appendFile($this->assetUrl('js/tesseract.js'));
+$this->headScript()->appendFile($this->assetUrl('js/matomo.js'));
 $this->trigger('view.layout');
 $userBar = $this->userBar();
 ?>