Support multiple GitHub SSH deploy keys (#568)

* add sshPublicKeysDirectoryPath and GIT_CONFIG_EXTENSIONS parameters that adds git configs and mounts .ssh/config and public keys to the container, in order to allow multiple sh deploy key trick by webplatform@ssh-agent

* remove sshPublicKeysDirectoryPath and GIT_CONFIG_EXTENSIONS from windows runner for now

action.yml

@@ -85,6 +85,10 @@ inputs:
     required: false
     default: ''
     description: 'SSH Agent path to forward to the container'
+  sshPublicKeysDirectoryPath:
+    required: false
+    default: ''
+    description: 'Path to a directory containing SSH public keys to forward to the container.'
   gitPrivateToken:
     required: false
     default: ''