Add analytics to App links

Author: ksheremet

index.html

@@ -117,7 +117,7 @@ <h3>Delern Flashcards</h3>
             <table>
                 <tr>
                     <td>
-                        <a target="_blank" href='https://play.google.com/store/apps/details?id=org.dasfoo.delern'>
+                        <a target="_blank" href='https://play.google.com/store/apps/details?id=org.dasfoo.delern&referrer=utm_source%3Ddasfoosite'>
                             <img alt='Get it on Google Play' src='https://play.google.com/intl/en_us/badges/images/generic/en_badge_web_generic.png'
                                 height='64px' />
                         </a>
@@ -160,7 +160,7 @@ <h3>CoctailsPro</h3>
             <table>
                 <tr>
                     <td>
-                        <a target="_blank" href='https://play.google.com/store/apps/details?id=ch.sheremet.katarina.cocktailspro'>
+                        <a target="_blank" href='https://play.google.com/store/apps/details?id=ch.sheremet.katarina.cocktailspro&referrer=utm_source%3Ddasfoosite'>
                             <img alt='Get it on Google Play' src='https://play.google.com/intl/en_us/badges/images/generic/en_badge_web_generic.png'
                                 height='64px' />
                         </a>
@@ -180,7 +180,7 @@ <h3>Advent Calendar</h3>
             <table>
                 <tr>
                     <td>
-                        <a target="_blank" href='https://play.google.com/store/apps/details?id=ch.womentechmakers.adventcalendar'>
+                        <a target="_blank" href='https://play.google.com/store/apps/details?id=ch.womentechmakers.adventcalendar&referrer=utm_source%3Ddasfoosite'>
                             <img alt='Get it on Google Play' src='https://play.google.com/intl/en_us/badges/images/generic/en_badge_web_generic.png'
                                 height='64px' />
                         </a>