update portacode

[dsyme]

This updates portacode.

• Some additional bugs with top-level mutable values have been fixed in the interpreter

• The command line to start the tool is now

  fabulous --watch --send
  

  which defaults to the localhost webhook URL.

Arguments:
   --watch           Watch the source files of the project for changes
   --webhook:<url>   Send the JSON-encoded contents of the PortaCode to the webhook
   --send            Equivalent to --webhook:http://localhost:9867/update

[TimLariviere]

Good. Seems to cover #306 as well. :)

Could you just revert the version number (Directory.Build.props and template.json) please?
I prefer to bump it only in the release PR.

Also I think LiveUpdate output need to be updated
https://github.com/fsprojects/Fabulous/blob/3474315534b0edee60f195df6f4f13f89e897a26/src/Fabulous.LiveUpdate/LiveUpdate.fs#L67-L82