Add badges to README.md

[kwankyu]

for those who want to play with Sage instantly, and also as a preparation for #36245.

See this REAME.md.

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[mkoeppe]

If we want to start with such badges, we should probably also add them for:

• gitpod as described in https://doc.sagemath.org/html/en/developer/workspace.html#gitpod
• our docker image
• https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/setting-up-your-repository/facilitating-quick-creation-and-resumption-of-codespaces#overview

[kwankyu]

This is the Binder badge

Are the other badges below comparable with the Binder badge in the sense of "click, wait, and run sage either on command line or in jupyter online"?

This starts to build sage from source.

This opens up an online platform where you can build sage from source.

For the docker, you run the docker image on your own local computer. Actually Binder is just a way to run the docker image online.

[kwankyu]

binder is completely free of charge.

gitpod seems free for the basic use for gitpod account owners.

codespaces seems free for me perhaps since I am a member of sagemath. Is this free also for casual visitors to our repo?

[mkoeppe]

I think Codespaces requires someone to pay for it. I haven't used it. @tobiasdiez may know more about it.

[kwankyu]

According to https://docs.github.com/en/get-started/learning-about-github/githubs-plans, codespaces is free of charge for public repositories with some limit in time and space.

[kwankyu]

The codespaces badge allows code editing but running Sage there requires building sage from source.

With more investigation, I see that the codespaces platform contains prebuilt sage, which is currently SageMath version 10.2.beta5, Release Date: 2023-09-27. This seems to be conda-based sage, defined by src/environment-dev.yml. I don't know why this is far behind the current version... (This seems the Sage built when I used the service last time.)

Anyway, as I said before, the codespaces is available right from the github interface. So we may omit this one.

[kwankyu]

I decided to add all three: binder, gitpod, codespaces. From README.md,

[kwankyu]

A link to the docker image is already in README:

https://github.com/sagemath/sage#sagemath-docker-images

[github-actions]

Documentation preview for this PR (built with commit 07a6fbc; changes) is ready! 🎉

[mkoeppe]

LGTM

[kwankyu]

Thanks!