fix: change type definitions to make inferring types of safeTry more strict

[3846masa]

In the current safeTry function, TypeScript cannot infer the type if the yielded Err and the Err returned by the generator function are different types.

interface FirstYieldError {
  name: 'FirstYieldError';
}
interface ReturnError {
  name: 'ReturnError';
}

// cannot infer the return type, but the return type is expected to be `Result<string, FirstYieldError | ReturnError>`
const result = safeTry(function*() {
  yield* ok<null, FirstYieldError>(null).safeUnwrap();
  return ok<string, ReturnError>('string');
});

In this PR, the type definition file will be changed so that TypeScript can correctly infer the return value of the safeTry function.

interface FirstYieldError {
  name: 'FirstYieldError';
}
interface ReturnError {
  name: 'ReturnError';
}

{
  // `Result<string, FirstYieldError | ReturnError>`
  const result = safeTry(function*() {
    yield* ok<null, FirstYieldError>(null).safeUnwrap();
    return ok<string, ReturnError>('string');
  });
}

{
  // As before, Generics accepts Value (T) and Error (E) type.
  const result = safeTry<string, FirstYieldError | ReturnError>(function*() {
    yield* ok<null, FirstYieldError>(null).safeUnwrap();
    return ok<string, ReturnError>('string');
  });
}

[m-shaka]

@supermacro
Hi!
I'm not the author, but I think this PR made a great improvement on DX. I would be really happy if you could check it 🙏