Add digital-preservation collection

[ross-spencer]

Please confirm this pull request meets the following requirements:

• I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• I am not the sole author or employee of a company who created either the topic I am modifying/adding or the collection entry I am modifying/adding.

Which change are you proposing?

• Suggesting edits to an existing topic or collection
• Curating a new topic or collection
• Something that does not neatly fit into the binary options above

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Editing an existing topic or collection

I'm suggesting these edits to an existing topic or collection:

• Image (and my file is *.png, square, dimensions 288x288, size <= 75 kB)
• Content (and my changes are in index.md)

Please replace this line with an explanation of why you think these changes should be made.

Curating a new topic or collection

• I've formatted my changes as a new folder directory, named for the topic or collection as it appears in the URL on GitHub (e.g. https://github.com/topics/[NAME] or https://github.com/collections/[NAME])
• My folder contains a *.png image (if applicable) and index.md
• All required fields in my index.md conform to the Style Guide and API docs: https://github.com/github/explore/tree/main/docs

Long-term preservation and archiving is important to all of us working digitally. The "industry" or "field" is young, and its open source status younger, but there are examplars of repositories that make a difference on GitHub and these, and I am sure others in future. I felt these are worth curating into a Collection with the hope it will inspire other developers and continue the momentum in existing repositories to keep working on them and improving them for bigger communities on GitHub.

Something that does not neatly fit into the binary options above

• My suggested edits are not about an existing topic or collection, or at least not a single one
• My suggested edits are not about curating a new topic or collection, or at least not a single one
• My suggested edits conform to the Style Guide and API docs: https://github.com/github/explore/tree/main/docs

Please replace this line with an explanation of your proposed changes.

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Please note: we will close your PR without comment if you do not check the boxes above and provide ALL requested information.

[tomthorogood]

@ross-spencer thank you for this contribution! It looks like the image you provided is failing validation because of how large it is. If you could please replace it with something scaled down to below 288x288px and also < 75kb, this can probably progress.

Thank you!

[ross-spencer]

Thanks @tomthorogood -- resized and pushed!