fix(android): use Locale.ROOT when changing case in java (#1152)

Not setting locale for language/country neutral operation may cause bug depending on the default locale.
See https://docs.oracle.com/javase/7/docs/api/java/util/Locale.html#ROOT

Note: I am just searching for toLowerCase() and toUppercase() in my project's dependencies and send the same PR, in order to potentially raise the awareness. Although I've seen the lack of explicit locale has caused issues for us, I am not sure if react-native-share is actually affected.

Example related issue: joltup/rn-fetch-blob#573

android/src/main/java/cl/json/RNShareModule.java

@@ -14,6 +14,7 @@
 import com.facebook.react.bridge.Callback;
 
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 
 import cl.json.social.EmailShare;
@@ -141,7 +142,7 @@ public String getName() {
     public Map<String, Object> getConstants() {
         Map<String, Object> constants = new HashMap<>();
         for (SHARES val : SHARES.values()) {
-            constants.put(val.toString().toUpperCase(), val.toString());
+            constants.put(val.toString().toUpperCase(Locale.ROOT), val.toString());
         }
         return constants;
     }