Add expo-keyboard-language native module

New Expo module that exposes keyboard language detection via a node
handle. On iOS it resolves the React Native view tag to the underlying
UITextField/UITextView and returns textInputMode.primaryLanguage (BCP 47
tag). Android and web return null for now.

https://claude.ai/code/session_01AMCp4M56WtFPz1pZtwgcvx

modules/expo-keyboard-language/expo-module.config.json

@@ -0,0 +1,9 @@
+{
+  "platforms": ["ios", "android"],
+  "ios": {
+    "modules": ["ExpoKeyboardLanguageModule"]
+  },
+  "android": {
+    "modules": ["expo.modules.keyboardlanguage.ExpoKeyboardLanguageModule"]
+  }
+}