Remove links to Gitpod, use Devcontainer file(s) instead

[briwylde08]

Gitpod is being sunset, so we need to remove all Gitpod links from the docs.

Should be done before April 2025.

[ElliotFriend]

• Use devcontainer.json in place of gitpod (example: https://github.com/brunogrbavac/soroban-examples/tree/main/.devcontainer)
• Replace in dev docs with codespaces link when ready

[anataliocs]

stellar/soroban-examples#371

[anataliocs]

Sample badges for replacing throughout the docs

HTML

<a href="https://github.com/codespaces/new?repo=stellar/soroban-examples&editor=web">
  <img src="https://github.com/codespaces/badge.svg" alt="Open in Codespaces">
</a>

Markdown

[![Open in Codespaces](https://github.com/codespaces/badge.svg)](https://github.com/codespaces/new?repo=stellar/soroban-examples&editor=web)

[anataliocs]

https://codespaces.new/stellar/soroban-examples/tree/migrate-to-devcontainers-poc

[anataliocs]

@briwylde08 Ok we merged in stellar/soroban-examples#371 should we start updating the links with Codespaces links?

[briwylde08]

I don't see why not! @ElliotFriend, any qualms?

[briwylde08]

@anataliocs Elliot and I are in agreement that let's do this thing!

[anataliocs]

Gitpod Replacement link 1:
Replacing Gitpod link in Stellar Docs README https://github.com/stellar/stellar-docs/pull/1514/files#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5L55

PR: #1514

[anataliocs]

#1516

@ElliotFriend @briwylde08 I think that's all the gitpod links? I may need to do another pass b/c I used find/replace global regex black magic to replace them all at once