fix #33: i18next-icu incompatible with react-i18next

I also folded in the fix from #32  to index.d.ts/README.md

Co-Authored-By: Jonas Woerlein <[email protected]>

README.md

@@ -40,9 +40,6 @@ i18next.use(ICU).init(i18nextOptions);
   // memoize if not having a lookup and just using the key fallback as value
   memoizeFallback: false,
 
-  // array or single object of loaded 'i18next-icu/locale-data
-  localeData: null,
-
   // which events should clear the cache, can be set to false or string of events separated by " "
   bindI18n: '',
 

i18nextICU.js

@@ -4427,7 +4427,13 @@
 
         try {
           if (!fc) {
-            fc = new IntlMessageFormat(res, lng, this.formats);
+            // without ignoreTag, react-i18next <Trans> translations with <0></0> placeholders
+            // will fail to parse, as IntlMessageFormat expects them to be defined in the
+            // options passed to fc.format() as { 0: (children) => string }
+            // but the replacement of placeholders is done in react-i18next
+            fc = new IntlMessageFormat(res, lng, this.formats, {
+              ignoreTag: true
+            });
             if (this.options.memoize && (this.options.memoizeFallback || !info || hadSuccessfulLookup)) setPath(this.mem, memKey, fc);
           }