Upgrade to Expo SDK 44

[wodin]

No description provided.

[wodin]

The first commit basically just upgrades the Expo parts of this repo to Expo SDK 44 and updates shadow-cljs and reagent versions.
The eas-build-post-install script is to automatically run shadow-cljs release app during Expo's EAS Build process.
The index.js file that just imports and re-exports app/index.js is because EAS Build currently doesn't support a non-default location for the entry point, as far as I know.
So just like before this change, the repository is basically like a newly created Expo app with some minimal shadow-cljs stuff added.

The second commit just explains how to build the app. The previous version of the README left this out.

The third commit removes the need to manually block Expo Web's fast refresh, which interferes with Shadow CLJS' reloading.

@thheller doesn't use Expo, so if someone has questions about this, post a question on https://forums.expo.dev

[thheller]

Thanks.