docs: use public folder in examples (#1601)

Author: kermanx

docs/builtin/components.md

@@ -295,11 +295,11 @@ Embed a video.
 ```md
 <SlidevVideo v-click autoplay controls>
   <!-- Anything that can go in a HTML video element. -->
-  <source src="myMovie.mp4" type="video/mp4" />
-  <source src="myMovie.webm" type="video/webm" />
+  <source src="/myMovie.mp4" type="video/mp4" />
+  <source src="/myMovie.webm" type="video/webm" />
   <p>
     Your browser does not support videos. You may download it
-    <a href="myMovie.mp4">here</a>.
+    <a href="/myMovie.mp4">here</a>.
   </p>
 </SlidevVideo>
 ```

docs/guide/syntax.md

@@ -51,7 +51,7 @@ This is the cover page.
 
 ---
 layout: center
-background: './images/background-1.png'
+background: /background-1.png
 class: 'text-white'
 ---
 
@@ -89,7 +89,7 @@ This is the cover page.
 ```yaml
 # The first yaml block will be treated as the frontmatter of that slide
 layout: center
-background: './images/background-1.png'
+background: /background-1.png
 class: 'text-white'
 ```