Add t function to TransProps types (#969)

* Add t function to TransProps types

* Add usage test

src/index.d.ts

@@ -40,6 +40,7 @@ export interface TransProps extends Partial<i18next.WithT> {
   parent?: React.ReactNode;
   tOptions?: {};
   values?: {};
+  t?: i18next.TFunction;
 }
 export function Trans(props: TransProps): any;
 

test/typescript/Trans.test.tsx

@@ -0,0 +1,56 @@
+import * as React from 'react';
+import { Trans, useTranslation } from 'react-i18next';
+
+function basic() {
+  return <Trans>Foo</Trans>;
+}
+
+function children() {
+  return (
+    <Trans>
+      <div />
+    </Trans>
+  );
+}
+
+function components() {
+  return <Trans components={[<div />]}>Foo</Trans>;
+}
+
+function count() {
+  return <Trans count={42}>Foo</Trans>;
+}
+
+function defaults() {
+  return <Trans defaults={'defaults'}>Foo</Trans>;
+}
+
+function i18n() {
+  const { i18n } = useTranslation();
+  return <Trans i18n={i18n}>Foo</Trans>;
+}
+
+function i18nKey() {
+  return <Trans i18nKey={'i18nKey'}>Foo</Trans>;
+}
+
+function ns() {
+  return <Trans ns={'ns'}>Foo</Trans>;
+}
+
+function parent() {
+  return <Trans parent={<div />}>Foo</Trans>;
+}
+
+function tOptions() {
+  return <Trans tOptions={{}}>Foo</Trans>;
+}
+
+function values() {
+  return <Trans values={{}}>Foo</Trans>;
+}
+
+function t() {
+  const { t } = useTranslation();
+  return <Trans t={t}>Foo</Trans>;
+}