Add StableNet

[hominlee-wemade]

This PR adds JSON metadata files for both StableNet Testnet and Mainnet(reservation) to the _data/chains folder following Chainlist conventions.

[github-actions]

You successfully submitted a PR! Due to the amount of PRs coming in: we will only look at PRs that the CI is happy with. We can also not hold your hand getting the CI green - just look how others that where merged did it and RTFM. So as long as there is any CI check that reports an error - no human will look at this. You might be able to ask for some support after supporting the project - e.g. by sending funds to lists.eth. When you fixed things after a requested change - then you also need to (re-)request a review.

[hominlee-wemade]

The Explorer 429 issue has been resolved and now returns 2XX for CI requests.
Please rerun the build. Thanks.

[hominlee-wemade]

The Explorer endpoint has been fixed and now consistently returns HTTP 2XX (no 429) for CI checks.
Please rerun the build when convenient. Thanks.