Fix #832: Markdown export has correct table sizes

[grepwood]

Export to Markdown will now generate appropriate tables for servers and models.

If a server on the list has an exclusive property, a column for it will be created, but for other servers that don't have it, it will generate an empty cell.

Likewise for models, if one field has an exclusive property that other fields don't have, the table will account for it, but leave empty cells for deficient fields.

• Tests pass
• ruff format
• README.md updated (if relevant)
•  CHANGELOG.md entry added

How do I run tests and ruff? What kind of change in README.md is expected?

[jochenchrist]

Please also add a test in https://github.com/datacontract/datacontract-cli/blob/main/tests/test_export_markdown.py

[simonharrer]

Why did you not follow hunyadi/md2conf#142 advice and use
instead? The issue is that having a table in html with too many columns is unreadable and hard to use.

[grepwood]

@simonharrer because I haven't tried it yet. As far as example files go (https://github.com/bitol-io/open-data-contract-standard/tree/main/docs/examples), I haven't come across one that would look terrible with many columns while working with datacontract-cli==0.10.31 with my patched exporter. I'll give it a shot tomorrow and let you know how it rolls.