* Enhanced Astro codespace support
Enhances the base devcontainer and Dockerfile to provide a smoother
development experience out of the box for contributors.
Adds a devcontainer per example so that we can add buttons on astro.new
that will launch users straight into the appropriate example app.
* Cleanup devcontainers and pin base image
* Update .devcontainer/example-welcome-message.txt
Co-authored-by: Samruddhi Khandale <skhandale@microsoft.com>
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Co-authored-by: Samruddhi Khandale <skhandale@microsoft.com>
