Switch back to official spacetime package

[Serraniel]

During the typescript migration (#48 ) spacetime was replaced with a customized version due to incomplete type definitions. I created a pull request with a fix in the spacetime repository: spencermountain/spacetime#256

As soon as this is merged and published we should switch back to the original spacetime package via npm.

[Serraniel]

See a6b7c3b.

[Serraniel]

I´ll set this as blocked, until the update is available.

[Serraniel]

An update for spacetime has been released today, so it can be changed to original version again now.

[Serraniel]

There has been some more changes in the typescript definitions on spacetime in 581f6a1e53718e12454bd7e94498785f5fb983f0 which break the new update.

I will try to report or fix the issue on the weekend to the project.