Changes the review workflow to a mermaid diagram

[omahane]

I was working on a session proposal for DrupalCon 2025 about Digital Public Goods when I looked at this repository of the Standard. I thought it might be worth changing the flowchart to use a generated diagram from text, rather than an image.

Changes proposed in this pull request:

• The flowchart that describes the submission workflow changes from an image to text, using the mermaid to leverage the Github rendering of the image. This makes the workflow more accessible, easier to change, easier to track across any future changes and more in line with the use of open source technologies.
• To make it easier to review, you can see the README.md in the PR branch of my fork: https://github.com/omahane/DPG-Standard/tree/diagram-change-to-mermaid

Propagation of Changes

Identify where of the following the proposed changes need to be propagated, and include the relevant pull request where appropriate:

• The README.md at the repository root appears to be only page with this flowchart. A different flowchart is on https://github.com/DPGAlliance/publicgoods-candidates/blob/main/help-center/dpg-review-policy.md, which could also be replicated with mermaid.

[kjetilk]

Just to say that I support the use of mermaid diagrams, since it allows for version control and patching of the diagram itself. And it renders well.

[ricardomiron]

Thanks for the contribution, this looks great!