feat: create script for updating lists of ecosystems

[G-Rath]

This introduces a new script to make it easier to ensure all "lists of ecosystems" within this codebase remain up to date, including:

• the table in docs/schema.md
• the Go constants being introduced in feat: create new Go packages #292
• the JSON schema in validation/schema.json (both the pattern and the enum being introduced in feat: create dedicated ecosystem name enum with all ecosystems #296)

To make it a bit easier, I've introduced a top-level ecosystems.json which is a map of defined ecosystems and a markdown description, sorted alphabetically (which the script also ensures) - I felt this was easier than trying to extract the list from markdown or another source, though it does mean double quotes need to be manually escaped.

I went with JSON as it can be read without requiring an external dependency, though if we use Python 3.11 we could switch to toml instead as that ships with tomllib