Feature Request: Export Command

Have you read a contributing guide?

• I have read CONTRIBUTING.md
• I have searched the existing requests and didn't find any that were similar
• I have considered creating a pull request instead and want to proceed

Clear and concise description of the problem

Hello! Thanks for all your effort. AnyType is amazing.

I find myself wanting the insurance of being able to export my data as a generally readable format (markdown). And I realize that the AnyType app lets you do this with a button, but I'd love to automate the process.

Having a command in the cli that does the same thing as the AnyType app would enable that, and I think it's a highly desired feature from searching through the community forums.

Suggested solution

# Suggested CLI...
Usage:
  anytype export [options] <space-id>

Export a space.
  
EXPORT OPTIONS
  -d, --destination DIR            The output destination (defaults to .)
  -f, --format FORMAT              The export format: (markdown, anyblock)
  -e, --encoding ENCODING          If exporting to anyblock, one of: (json, protobuf)
  --files                          Include files
  --archived                       Include archived
  -a, --all                        Include files and archived objects

Alternative

No response

Additional context

If I got a briefing on how exporting works in the app I could try to contribute a pull request, but I'm totally new to this codebase so i'm not sure where to start.

Start by tracing how the anytype-cli registers commands and handles a space-id, then investigate how the AnyType app performs space export. Define the command's destination, format, encoding, files, and archived options from the request, and consider how markdown, anyblock JSON, and protobuf output should be verified.