Server Node 18 support

Hi Speckle server developers,

A short note to say that we will shortly be upgrading development branches of Speckle server to Node 18.
This change to Speckle will affect anyone who is actively developing on the latest commits of Speckle server. It should not affect anyone else at this time.

The reason for this change is that although Node 16 is still being updated with security patches by the upstream Node project, Node 18 is the current Long Term Support (LTS) version of Node. To continue receiving bug fixes and support beyond security patches, an upgrade is required.

Happy coding!

The Speckle Team