[Feat][Doc] Refactor and update the format specification document

[acezen]

Proposed changes

Refactor and update the format specification document

• Add concepts to explain relevant concepts and terms.
• Refine file-format.rst to give more detail of GraphAr format
• Update the status: c++ support Date and Timestamp
• Add format & libraries feature update workflow to contributing guide

  Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [x] I have read the CONTRIBUTING doc
• [x] I have signed the CLA
• [ ] Lint and unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (if appropriate)

Further comments

close #362

[Thespica]

Hi, @acezen . I think we can highlight the benefits of splitting vertices/edges into chunks and splitting properties into property_groups (why we split that) for a little list, like:

1. Random access querying without reading all data from the file.
2. Appending data without modifying the existing files(or need only modifying the last chunk).

Maybe the third point: convenience for parallel reading.

[acezen]

Looks cool! One question: as I see, Timestamp and Date are already supported in #398, maybe we can update status.rst in this PR? Or it will be a separated PR?

Thanks for pointing out, I will update the status.rst in this PR.