docs: Add a few code lang labels, minor cleanup

src/docs/markdown/caddyfile/matchers.md

@@ -110,7 +110,7 @@ Defining a matcher with a unique name gives you more flexibility, allowing you t
 
 or, if there is only one matcher in the set:
 
-```
+```caddy-d
 @name ...
 ```
 
@@ -130,7 +130,7 @@ This proxies only the requests that have a header field named "Connection" conta
 
 If the matcher set consists of only one matcher, a one-liner syntax also works:
 
-```
+```caddy-d
 @post method POST
 reverse_proxy @post localhost:6001
 ```