Add codespaces devcontainer config

[snehankekre]

Adds a codespaces devcontainer config so that users can run the app on GitHub codespaces. Once the devcontainer is created, the app dependencies are installed, and the Chatbot.py app is auto launched.

[JoshuaC215]

This is so cool!

When I tried opening it via this link and it started a docker image build that took several minutes.

Is there a way we could optimize this? @sfc-gh-bholt mentioned there were some pre-built images that codespaces keeps warm - if we could swap this to use one of those I think the startup time might be several minutes faster.

I also wonder if there's a way to auto-launch the preview app 🤔 but maybe something to explore in a separate PR.

Adding a couple of links for reference (so I can find them later):

• https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/setting-up-your-repository/facilitating-quick-creation-and-resumption-of-codespaces
• https://docs.github.com/en/codespaces/developing-in-codespaces/forwarding-ports-in-your-codespace
• https://github.blog/changelog/2022-10-20-introducing-the-codespaces-simple-browser/

[sfc-gh-jcarroll]

@sfc-gh-cfrasca