add file.name(), file.stem() & add 'path' to pack info & add start_coroutine()

doc/en/scripting/builtins/libpack.md

@@ -83,6 +83,7 @@ pack.get_info(packid: str) -> {
   creator: str,
   description: str,
   version: str,
+  path: str,
   icon: str, -- not available in headless mode
   dependencies: optional strings array
 }