fix: include typescript typings

[jtomaszewski]

I see index.d.ts is included in the github repo, but it is not present in the npm package - see https://www.npmjs.com/package/hardtack?activeTab=code for proof . This makes TypeScript have no type declarations at all for hardstack currently.

Could we publish the package again, but with the typings inside of it?

This is probably regression caused by 1d21b22#diff-7ae45ad102eab3b6d7e7896acd08c427a9b25b346470d7bc6507b6481575d519L7 .

P.S. the "types" property in the package.json is not needed, because as said in https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#including-declarations-in-your-npm-package :

if your main declaration file is named index.d.ts and lives at the root of the package (next to index.js) you do not need to mark the types property