feature: support MetaMask third-party login for mobile browser too in Casdoor

[hsluoyz]

Now we already support MetaMask login in PC: https://casdoor.org/docs/provider/web3/metamask/ via MetaMask extension in Chrome. But we don't support MetaMask login in mobile phones.

So we also need to support it in mobile browsers, like Android Chrome, Apple Safari, etc.

You can try this demo site in mobile phone: https://metamask.github.io/test-dapp/ , the "CONNECT" button will try to redirect to the MetaMask app in mobile phone.

[casbin-bot]

@tangyang9464 @JalinWang @imp2002

[hsluoyz]

The PR: #2844 has been reverted because it causes yarn build too slow