feat: respect working_directory for files globs; add input and tests (#667)

action.yml

@@ -27,6 +27,9 @@ inputs:
   files:
     description: "Newline-delimited list of path globs for asset files to upload"
     required: false
+  working_directory:
+    description: "Base directory to resolve 'files' globs against (defaults to job working-directory)"
+    required: false
   overwrite_files:
     description: "Overwrite existing files with the same name. Defaults to true"
     required: false