refs #15440 [fid] add matomo opt-out iframe

* use fid-matomo url
* customize font and colors

themes/fid/templates/fid/user/matomo.phtml

+<?php $optOutUrl = "https://fid-matomo.ub.uni-leipzig.de/index.php?module=CoreAdminHome&action=optOut"
+    . "&backgroundColor=$backgroundColor"
+    . "&fontColor=$fontColor"
+    . "&fontSize=$fontSize"
+    . "&fontFamily=$fontFamily"
+    . "&language=$language"
+    . "&SiteId=1"
+?>
+
+<iframe
+    id="matomo" name="matomo"
+    src="<?=$optOutUrl?>"
+    frameborder="0"
+    scrolling="no">
+</iframe>
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