docs: add latest finschia mainnet/testnet information (backport #400)

[mergify]

Description

• Add latest finschia mainnet, ebony testnet information including below

  • Public endpoints
  • Genesis file download links
  • Testnet Faucet information
  • Example CLIs and REST APIs

• View: https://github.com/jaeseung-bae/finschia/blob/docs/finschia-io/README.md

Motivation and context

How has this been tested?

Screenshots (if appropriate):

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.

---

This is an automatic backport of pull request #400 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 35e3b48 has failed:

On branch mergify/bp/release/v4.0.x/pr-400
Your branch is up to date with 'origin/release/v4.0.x'.

You are currently cherry-picking commit 35e3b48.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   README.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally