Enable strict type checking and fix types

[daveallie]

Details

• Enable TypeScript strict type checking
  • Any consumer of this library who uses strict will have to currently either ignore the library code (as the types are incorrect) or patch the types, by enabling strict in the Nutrient library, we can allow strict consumers to use the library without overrides
  • Additionally, it catches a handful more type issues which exist within the TypeScript code.
• Fixed up some types, for example, there are types like pdfObjectId?: number = null which is completely invalid as pdfObjectId should be either a number or undefined.
  • Ran yarn build to rebuild the JS

Acceptance Criteria

• When approved, right before merging, rebase with master and increment the package version in package.json, package-lock.json, samples/Catalog/package.json, samples/Catalog/yarn.lock, samples/NativeCatalog/package.json, and samples/NativeCatalog/yarn.lock (see example commit: b32b4ed).
• Create a new release (and tag) with the new package version (see https://github.com/PSPDFKit/react-native/releases).

[daveallie]

Additionally, would love if the package could move off Yarn 1 onto Yarn 4, it's a bit painful to develop against as it is currently.