fix: Add syntax highlighting to code blocks

ssh/using_a_public_key_to_login.md

@@ -1,11 +1,11 @@
 You can generate authentication keys and use it with ssh to login. First run the below command if you don't have any (it won't overwrite if you already have one):
 
-```
+```bash
 ssh-keygen
 ```
 
 Then copy your public key to remote server with this:
-```
+```bash
 ssh-copy-id name@host
 ```