add Plausible server config (#422)

Author: hahnbeelee

integrations/analytics/plausible.mdx

@@ -6,15 +6,17 @@ Add your site's domain to `mint.json` to send analytics to Plausible.
 
 <Info>
 
-    Do not include `http://` or `https://` with your domain.
+    Do not include `https://` for the domain or server.
+
 </Info>
 
 <CodeGroup>
 
 ```json Analytics options in mint.json
 "analytics": {
     "plausible": {
-        "domain": "required"
+        "domain": "required",
+        "server": "optional"
     }
 }
 ```