`app` object unrecognized in `:theme_app_extension` config

[mmorissette]

Support for the new app liquid object was added as part of #566. However running theme-check with the theme-app-extension config still reports an error.

➜  theme-extension git:(main) ✗ theme-check -C :theme_app_extension
Checking . ...

blocks/hello.liquid:7: error: UndefinedObject: Undefined object `app`.
	{{ app.metafields.features.test }}
	  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Same happens when running from shopify CLI

➜  theme-extension git:(main) ✗ shopify extension check
Checking . ...

blocks/hello.liquid:7: error: UndefinedObject: Undefined object `app`.
	{{ app.metafields.features.test }}
	  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Unsure if the problem is with the implementation of support for app object or with loading the correct config from the command line.

[mgmanzella]

#566 wasn't live in production until we shipped v1.10.3 of theme-check today. this version of theme-check is now available in shopify-cli 2.19.0

the latest version of theme-check appears to fix this linting issue