Fix Android React Native environment shims which crash on normalizing…

… Korean test (ethers-io#1298).

packages/shims/src/index.js

@@ -12,9 +12,19 @@
         var forms = ["NFD", "NFC", "NFKD", "NFKC"];
         for (var i = 0; i < forms.length; i++) {
             try {
+                // Simple test that catches invalid normalization
                 if ("test".normalize(forms[i]) !== "test") {
                     throw new Error("failed to normalize");
                 }
+
+                // Some platforms seem to only fail when normalizing
+                // specific code planes, so add those here as they
+                // come up.
+                //               "hangul"
+                const checks = [ "\ud55c\uae00" ];
+                for (var j = 0; j < checks.length; j++) {
+                    checks[j].normalize(forms[i]);
+                }
             } catch(error) {
                 missing.push(forms[i]);
             }