Refactor sliding modal, combine options when passing

Riot/Modules/SlidingModal/SlidingModalContainerView.swift

@@ -56,6 +56,8 @@ class SlidingModalContainerView: UIView, Themable, NibLoadable {
         }
     }
     
+    var centerInScreen: Bool = false
+    
     // MARK: Outlets
     
     @IBOutlet private weak var dimmingView: UIView!
@@ -130,7 +132,11 @@ class SlidingModalContainerView: UIView, Themable, NibLoadable {
         if UIDevice.current.userInterfaceIdiom == .pad {
             self.contentViewBottomConstraint.constant = (UIScreen.main.bounds.height + self.dismissContentViewBottomConstant) / 2
         } else {
-            self.contentViewBottomConstraint.constant = 0
+            if centerInScreen {
+                contentViewBottomConstraint.constant = (bounds.height - contentViewHeightConstraint.constant)/2
+            } else {
+                contentViewBottomConstraint.constant = 0
+            }
         }
     }