Consider support deep links other than mailto:// and tel://

Hi,

There are some legitimate use cases where opening deep links of various protocols, e.g., `fb://`, `messenger://` should be able to open corresponding apps.

However, [this web view only supports `mailto` and `tel` protocols](https://github.com/CRAlpha/react-native-wkwebview/blob/master/ios/RCTWKWebView/RCTWKWebView.m#L468).

It would be great if all protocols other than `http` and `https` are allowed, and app developers could set [LSApplicationQueriesSchemes](https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/LaunchServicesKeys.html#//apple_ref/doc/plist/info/LSApplicationQueriesSchemes) to meet their needs.

Probably something like:

```
if (![scheme isEqualToString:@"http"] && ![scheme isEqualToString:@"https"]) {
if ([app canOpenURL:url]) {
[app openURL:url];
decisionHandler(WKNavigationActionPolicyCancel);
return;
}
}
```

Seems simple.
If this looks good to you, I can submit a PR.
Thanks!