#81 add video issue doc in live-design-demo section

web/components/landingpage/motion/live-design-demo/ios-15-safari-video-issue.md

@@ -0,0 +1,43 @@
+## Why use html5 video instead of react-player in this place?
+
+_This document is explaining how to use pure HTML5 video instead of react-player, which is the video player used in the project only in the live-design-demo section._
+
+While updating to ios 15 version, some video stuttering in safari was found. For example, let's say you are using the tag below.
+
+```typescript
+<ReactPlayer
+  url={require("public/videos/video.mp4")}
+  loop
+  playing
+  muted
+  playsinline
+  config={{
+    file: {
+      attributes: {
+        preload: "auto",
+      },
+    },
+  }}
+/>
+```
+
+All use the same code as in the example, except for the url, but it has been confirmed that the problem occurs only in the specific location _(the video play only when the video is not visible on the screen)_.
+
+I've tried several tests, such as changing the parent's position, but it's still there. But when I used the video tag in pure html5 there was no problem.
+Below is an example used.
+
+```typescript
+<video
+  src={require("public/videos/video.mp4")}
+  autoPlay
+  muted
+  loop
+  playsInline
+  preload="auto"
+/>
+```
+
+So, until the video problem is stable in ios 15 safari, the problematic video from `live-design-demo` is replaced with pure html5 `video` tag.
+
+<!--
+그리하여 ios 15 safari에서 비디오 문제가 안정되기 전까지는 문제가 있는 live-design-demo 의 비디오는 순수 html5 비디오 태그로 대치합니다. -->