chore: package should export package.kson

[jthegedus]

Describe the Bug

If you don't export package.json then tooling can't access it. There's some tooling like rollup-plugin-svelte that tries to access the package.json of every package (e.g. to determine if it's a Svelte package in that case) and you will get an error if it's not exported
source - sveltejs/kit#2351 (comment)

Steps to Reproduce

NA

Expected Behaviour

package.json is also exported by the package.

svelte-adapter-firebase version

0.11.1

sveltejs/kit version

1.0.0-next.165