[native] added react-native-webview to support SIWE

Summary: added react-native-webview to support sign in with ethereum on native. related linear task - parent SIWE task

Test Plan: compile/run comm with xcode to ensure adding webview didn't break anything

Reviewers: abosh, atul, ashoat

Reviewed By: ashoat

Subscribers: abosh, atul, adrian, tomek, ashoat, varun, jacek

Differential Revision: https://phab.comm.dev/D4959