export typedefs

[ruin403]

Currently, the typedefs in the @triton-one/yellowstone-grpc npm package are inaccessible in some project configurations:

Could not find a declaration file for module '@triton-one/yellowstone-grpc'. '/project/node_modules/@triton-one/yellowstone-grpc/dist/esm/index.js' implicitly has an 'any' type.
  There are types at '/project/node_modules/@triton-one/yellowstone-grpc/dist/types/index.d.ts', but this result could not be resolved when respecting package.json "exports". The '@triton-one/yellowstone-grpc' library may need to update its package.json or typings.

This PR adds the typedefs to the export section in package.json.