Using SSH_AUTH_SOCK (ssh agent forwarding) to pull upm private repos (#256)

* using SSH_AUTH_SOCK (ssh agent forwarding) to pull upm private repos

* sshAgent as input parameter

* yarn run prettier --write "src/**/*.{js,ts}"

* yarn run lint --fix && yarn build

* fixed compilation after rebase

* removed RUN apt-get update && apt-get install -y openssh-client. This change needs to be done upstream. See game-ci/docker#117

action.yml

@@ -106,6 +106,10 @@ inputs:
 
       Parameters must start with a hyphen (-) and may be followed by a value (without hyphen).
       Parameters without a value will be considered booleans (with a value of true).
+  sshAgent:
+    required: false
+    default: ''
+    description: 'SSH Agent path to forward to the container'
   chownFilesTo:
     required: false
     default: ''