Add minimal dtool dataset metadata schema

[jotelha]

I would like to create a universal JSON schema for validating metadata attached to dtool datasets (see articles https://peerj.com/articles/6562/, https://doi.org/10.1371/journal.pone.0306100, and dserver demonstrator at https://demo.dtool.dev).

I have no experience with creating schema, but I believe these changes should be a minimal starting point.

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.

[jotelha]

My apologies for cluttering this PR, I opened it a little early.

I have renamed the schema files to a versioned scheme.

Now, I have somehow messed up and cannot get rid of this error

$ node ./cli.js check 
===== VALIDATE PRECONDITIONS =====
---
>> Failed to find a schema file at "src/schemas/json/dtool-dataset-metadata.json"
---
Error
    at onTestDir (file:///mnt/dat2/git/dtool/schemastore/cli.js:839:29)
    at async Promise.all (index 0)
    at async assertFileSystemIsValid (file:///mnt/dat2/git/dtool/schemastore/cli.js:831:5)
    at async Object.taskCheck (file:///mnt/dat2/git/dtool/schemastore/cli.js:564:3)
    at async file:///mnt/dat2/git/dtool/schemastore/cli.js:1560:5

anymore, which I do not quite understand, as nothing in the tree points to the initial dtool-dataset-metadata.json without version suffix anymore.

Apologies again, some help would be much appreciated. Thank you!

[hyperupcall]

anymore, which I do not quite understand, as nothing in the tree points to the initial dtool-dataset-metadata.json without version suffix anymore.

@jotelha Thanks for reporting! The error came from the name of the test directory: src/test/dtool-dataset-metadata. I fixed the directory name and updated the error message so there's more information for the next person that potentially stumbles upon this

Sorry for getting to this late, feel free to let me know if I missed anything!