document how to express a % character

Rich-Harris · Rich-Harris · commit 3b295b6d46cf · 2022-07-08T11:07:13.000-04:00
diff --git a/documentation/docs/02-routing.md b/documentation/docs/02-routing.md
@@ -415,3 +415,5 @@ assert.equal(
 	'@[username].svelte'
 );
 ```
+
+To express a `%` character, use `%25`, otherwise the result will be malformed.
