Add sponsored by Thunderbird label to translations

app/ui/archiveTile.js

@@ -597,7 +597,7 @@ module.exports.preview = function(state, emit) {
               height="30"
             />
           </svg>
-          Sponsored by Thunderbird
+          ${state.translate('sponsoredByThunderbird')}
         </a>
       `
     : '';

public/locales/en-CA/send.ftl

@@ -147,3 +147,5 @@ shareLinkButton = Share link
 shareMessage = Download “{ $name }” with { -send-brand }: simple, safe file sharing
 trailheadPromo = There is a way to protect your privacy. Join Firefox.
 learnMore = Learn more.
+
+sponsoredByThunderbird = Sponsored by Thunderbird

public/locales/en-GB/send.ftl

@@ -152,3 +152,5 @@ shareLinkButton = Share link
 shareMessage = Download “{ $name }” with { -send-brand }: simple, safe file sharing
 trailheadPromo = There is a way to protect your privacy. Join Firefox.
 learnMore = Learn more.
+
+sponsoredByThunderbird = Sponsored by Thunderbird

public/locales/en-US/send.ftl

@@ -143,3 +143,5 @@ shareLinkButton = Share link
 # $name is the name of the file
 shareMessage = Download “{ $name }” with { -send-brand }: simple, safe file sharing
 learnMore = Learn more.
+
+sponsoredByThunderbird = Sponsored by Thunderbird

public/locales/nl/send.ftl

@@ -152,3 +152,5 @@ shareLinkButton = Koppeling delen
 shareMessage = Download ‘{ $name }’ met { -send-brand }: eenvoudig, veilig bestanden delen
 trailheadPromo = Er is een manier om uw privacy te beschermen. Doe mee met Firefox.
 learnMore = Meer info.
+
+sponsoredByThunderbird = Gesponsord door Thunderbird