docs: add example link. (#1582) (#1583)

Co-authored-by: Kevin <71524776+freemankevin@users.noreply.github.com>
diff --git a/docs/en/latest/tutorials/mtls.md b/docs/en/latest/tutorials/mtls.md
index 605926a..1b7e334 100644
--- a/docs/en/latest/tutorials/mtls.md
+++ b/docs/en/latest/tutorials/mtls.md
@@ -107,7 +107,9 @@
 
 ApisixTls requires a secret which field `cert` and `key` contains the certificate and private key.
 
-A secret yaml containing the certificate mentioned above [is here](https://github.com/apache/apisix-ingress-controller/blob/master/docs/en/latest/tutorials/mtls/server-secret.yaml). In this guide, we use this as an example.
+The keys and certificates used in the examples [are here](https://github.com/apache/apisix-ingress-controller/tree/master/docs/en/latest/tutorials/mtls).
+
+In this guide, we use this as an example.
 
 ```bash
 kubectl apply -f ./mtls/server-secret.yaml -n default
@@ -156,6 +158,8 @@
 
 Like `server-secret`, we will create a `client-ca-secret` to store the CA that verify the certificate client presents.
 
+The keys and certificates used in the examples [are here](https://github.com/apache/apisix-ingress-controller/tree/master/docs/en/latest/tutorials/mtls).
+
 ```bash
 kubectl apply -f ./mtls/client-ca-secret.yaml -n default
 ```
@@ -202,6 +206,8 @@
 
 Now, we need to transfer our client cert to the APISIX container to verify the mTLS functionality.
 
+The keys and certificates used in the examples [are here](https://github.com/apache/apisix-ingress-controller/tree/master/docs/en/latest/tutorials/mtls).
+
 ```bash
 # Transfer client certificate
 kubectl -n apisix cp ./user.key <APISIX_POD_NAME>:/tmp/user.key