ensure defaults for configuration values

Signed-off-by: Eli Uriegas <eliuriegas@fb.com>

action.yml

@@ -9,8 +9,13 @@ inputs:
     description: 'Destination path'
     required: false
   s3-bucket:
-    description: 'S3 bucket to pull from'
-    required: false
+    description: >
+      S3 Bucket to use to put your artifacts in, typically something like "gha-artifacts"
+    default: 'gha-artifacts'
+  region:
+    description: >
+      Region your s3 bucket is in
+    default: 'us-east-1'
 runs:
   using: 'node12'
   main: 'dist/index.js'