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

src/model/input.ts

@@ -178,6 +178,10 @@ class Input {
     return Input.getInput('sshAgent') || '';
   }
 
+  static get sshPublicKeysDirectoryPath(): string {
+    return Input.getInput('sshPublicKeysDirectoryPath') || '';
+  }
+
   static get gitPrivateToken(): string | undefined {
     return Input.getInput('gitPrivateToken');
   }