feat(SplitButton): add flip prop support

src/SplitButton.tsx

@@ -19,6 +19,7 @@ export interface SplitButtonProps
   title: React.ReactNode;
   toggleLabel?: string;
   type?: ButtonType;
+  flip?: boolean;
 }
 
 const propTypes = {
@@ -74,6 +75,13 @@ const propTypes = {
    */
   rootCloseEvent: PropTypes.string,
 
+  /**
+   * Allow Dropdown to flip in case of an overlapping on the reference element. For more information refer to
+   * Popper.js's flip [docs](https://popper.js.org/docs/v2/modifiers/flip/).
+   *
+   */
+  flip: PropTypes.bool,
+
   /** @ignore */
   bsPrefix: PropTypes.string,
   /** @ignore */
@@ -114,6 +122,7 @@ const SplitButton = React.forwardRef<HTMLElement, SplitButtonProps>(
       menuRole,
       renderMenuOnMount,
       rootCloseEvent,
+      flip,
       ...props
     },
     ref,
@@ -146,6 +155,7 @@ const SplitButton = React.forwardRef<HTMLElement, SplitButtonProps>(
         role={menuRole}
         renderOnMount={renderMenuOnMount}
         rootCloseEvent={rootCloseEvent}
+        flip={flip}
       >
         {children}
       </Dropdown.Menu>