chore(l10n): update Spanish translations

Currently translated at 100.0% (94 of 94 strings)

Translation: Fossify/Calculator
Translate-URL: https://hosted.weblate.org/projects/fossify/calculator/es/
Via: Weblate

Author: elliecolorado

app/src/main/res/values-es/strings.xml

@@ -92,4 +92,6 @@
     <string name="unit_temperature_kelvin">Kelvin</string>
     <string name="unit_temperature_rankine">Rankine</string>
     <string name="unit_temperature_fahrenheit">Fahrenheit</string>
+    <string name="unit_volume_customary_cup_us">Taza común (EEUU)</string>
+    <string name="unit_volume_legal_cup_us">Taza legal (EEUU)</string>
 </resources>