[docs] minor UX smoothing

- make toggling the push flyout slightly less annoying/jumpy

- by re-scrolling/re-centering on the toggle button

src-docs/src/views/flyout/flyout_push.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useState, MouseEvent } from 'react';
 
 import {
   EuiFlyout,
@@ -63,7 +63,25 @@ export default () => {
         compressed
       />
       <EuiSpacer size="m" />
-      <EuiButton onClick={() => setIsFlyoutVisible((visible) => !visible)}>
+      <EuiButton
+        onClick={(event: MouseEvent) => {
+          setIsFlyoutVisible((visible) => !visible);
+
+          // Minor UX smoothing - make sure the flyout toggle button stays anchored
+          // in the same spot in the user viewport once layout is done shifting
+          const button = event.target as HTMLButtonElement;
+          const initialTop = button.getBoundingClientRect().top;
+          setTimeout(() => {
+            const newTop = button.getBoundingClientRect().top;
+            const scrollDiff = newTop - initialTop;
+            window.scrollTo({
+              top: window.scrollY + scrollDiff,
+              left: window.scrollX,
+              behavior: 'smooth',
+            });
+          }, 50);
+        }}
+      >
         Toggle pushed flyout
       </EuiButton>
       {flyout}