Add Estonian (et, Eesti) to the langs list

Its first translations were added in the previous commit, pulled from
Weblate.

app/src/main/res/values/donottranslate.xml

@@ -42,6 +42,7 @@
         <item>el</item>
         <item>eo</item>
         <item>es</item>
+        <item>et</item>
         <item>eu</item>
         <item>fa</item>
         <item>fi</item>
@@ -92,6 +93,7 @@
         <item>Ελληνικά</item>
         <item>Esperanto</item>
         <item>Español</item>
+        <item>Eesti</item>
         <item>Euskara</item>
         <item>ﻑﺍﺮﺳی</item>
         <item>Suomi</item>