Fix heading levels

The nearest ancestor level for these headings is H2.  Thus, to avoid a
gap, these headings have been changed from H4 to H3.

Author: jonathanhefner

docs/introduction.mdx

@@ -45,7 +45,7 @@ flowchart LR
 
 Choose the path that best fits your needs:
 
-#### Quick Starts
+### Quick Starts
 
 <CardGroup cols={2}>
   <Card title="For Server Developers" icon="bolt" href="/quickstart/server">
@@ -60,7 +60,7 @@ Choose the path that best fits your needs:
   </Card>
 </CardGroup>
 
-#### Examples
+### Examples
 
 <CardGroup cols={2}>
   <Card title="Example Servers" icon="grid" href="/examples">