add schemas for PDM

[jvllmr]

• added pdm.json
• added partial-pdm.json

closes #3465

[henryiii]

I think the plan is to name partial schemas (for tool tables) as partial-<tool>, see #3422.

[hyperupcall]

Thanks for your contribution! Yeah this isn't quite documented yet - that issue has more information - the gist of it is:

• If a schema represents an existing project, that could be its own file (even if INI), then keep the name the same (what is already done)
• If the schema cannot be its own file, prefixpartial- (partial-mypy.json). If later the project supports a stanadlone config file, we can always $ref the partial.

Since it looks like the current "PDM Pyproject" project doesn't have it's own configuration file (pdm.toml looks to be an entirely different schema), then best would be to name it as partial-pdm.json

[jvllmr]

Thanks for the hint. Will change it asap.

[jvllmr]

I guess the PR is ready for review now. Let me know if you find issues.

[hyperupcall]

awesome, thank you