docs: add example for headers

Author: ctron

Trunk.toml

@@ -53,6 +53,8 @@ ws_protocol = "ws"
 # The certificate/private key pair to use for TLS, which is enabled if both are set.
 # tls_key_path = "self_signed_certs/key.pem"
 # tls_cert_path = "self_signed_certs/cert.pem"
+# Additional headers to send. NOTE: header names must be valid HTTP headers.
+# headers = { "X-Foo" = "bar" }
 
 [clean]
 # The output dir for all final assets.