Add features smlnj and VIM from souce.

[MartinAskestad]

What type of PR is this?

• Add a new dev container collection
• Update to an existing dev container collection
• Documentation/spec update
• Other containers.dev site update (UX, layout, etc)

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Description

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Collection checklist

If your PR contributes a new collection, please utilize this checklist:

• Collection name
• Maintainer name
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• Repository URL
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• I acknowledge that this collection provides new functionality, distinct from the existing collections part of this index.