Add "edit in playground" to stlite embeds

[arnaudmiribel]

Changes

Preview docs

• You can now hit "Edit in playground" to try out an extra with source code in Streamlit playground
• Refactored extras metadata to merge __experimental_playground__ (deprecated) and __stlite__. Merged into __playground__
• Docs now use __playground__ and also redirect folks to the playground if they want to edit the embedded stlite
• Edited one or two extras to unlock their playgrounds, hopefully - it's hard to test since stlite can't use packages from source, I basically need a version upgrade to test this out eheh

[netlify]

✅ Deploy Preview for streamlit-extras-docs ready!

Name	Link
🔨 Latest commit	1c5ae5e
🔍 Latest deploy log	https://app.netlify.com/sites/streamlit-extras-docs/deploys/672362d364693d00085b7236
😎 Deploy Preview	https://deploy-preview-217--streamlit-extras-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.