ios: add ability to control deep / universal linking

Since the SDK may be embedded with other apps, we need to recognize our custom
URL scheme and universal links in order to tell the user if we will process the
request or not.

Make them configurable with sane defaults.

ios/app/src/AppDelegate.m

         [Fabric with:@[[Crashlytics class]]];
     }
 
-    // Set the conference activity type defined in this application.
-    // This cannot be defined by the SDK.
     [JitsiMeet sharedInstance].conferenceActivityType = JitsiMeetConferenceActivityType;
+    [JitsiMeet sharedInstance].customUrlScheme = @"org.jitsi.meet";
+    [JitsiMeet sharedInstance].universalLinkDomains = @[@"meet.jit.si", @"beta.meet.jit.si"];
+
     [[JitsiMeet sharedInstance] application:application didFinishLaunchingWithOptions:launchOptions];
 
     return YES;

ios/sdk/src/JitsiMeet.h

 #import <JitsiMeet/JitsiMeetView.h>
 #import <JitsiMeet/JitsiMeetViewDelegate.h>
 
+
 @interface JitsiMeet : NSObject
 
 @property (copy, nonatomic, nullable) NSString *conferenceActivityType;
+@property (copy, nonatomic, nullable) NSString *customUrlScheme;
+@property (copy, nonatomic, nullable) NSArray<NSString *> *universalLinkDomains;
 
 #pragma mak - This class is a singleton
 

ios/sdk/src/JitsiMeet.m

         return YES;
     }
 
+    if (![_customUrlScheme isEqualToString:url.scheme]) {
+        return NO;
+    }
+
     return [JitsiMeetView loadURLInViews:@{ @"url" : url.absoluteString }];
 }
 
 
     if ([activityType isEqualToString:NSUserActivityTypeBrowsingWeb]) {
         // App was started by opening a URL in the browser
-        return @{ @"url" : userActivity.webpageURL.absoluteString };
+        NSURL *url = userActivity.webpageURL;
+        if ([_universalLinkDomains containsObject:url.host]) {
+            return @{ @"url" : url.absoluteString };
+        }
     } else if ([activityType isEqualToString:@"INStartAudioCallIntent"]
                || [activityType isEqualToString:@"INStartVideoCallIntent"]) {
         // App was started by a CallKit Intent
     return nil;
 }
 
+#pragma mark - Property getter / setters
+
+- (NSString *)customUrlScheme {
+    return _customUrlScheme ? _customUrlScheme : @"org.jitsi.meet";
+}
+
+- (NSArray<NSString *> *)universalLinkDomains {
+    return _universalLinkDomains ? _universalLinkDomains : @[@"meet.jit.si"];
+}
+
 #pragma mark - Private API methods
 
 - (RCTBridge *)getReactBridge {