web-forms vue component package doesn't export types

### Description

When creating the demo app in a separate repo imports from `@getodk/web-forms` complained about being unable to find types while `@getodk/xforms-engine` did not.

I think it's because
1. we're missing `"types": "./dist/index.d.ts",` from the package.json
2. we're missing `"declaration": true` from the tsconfig.json

Inspect package.json and tsconfig.json in the web-forms package, then compare the type-export setup with @getodk/xforms-engine. Run the separate demo app or an equivalent import check, and consider the issue done when imports from @getodk/web-forms resolve its generated TypeScript declarations without errors.

Written by the indexing model from the issue text.