Add superproductivity

[Mustache-Games]

Please confirm this pull request meets the following requirements:

• I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• This change is not self-promotion.

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

This PR curates the new topic superproductivity.

superProductivity is a popular, actively maintained, fully open-source (MIT) advanced to-do list and time-tracking app with over 13 k stars on its main repository (johannesjo/super-productivity). It offers native clients for Windows, macOS, Linux, Android, and a web version, and is especially loved by developers for its deep Jira, GitHub Issues, GitLab, and OpenProject integrations, Pomodoro/timeboxing support, break reminders, and complete offline/privacy focus.

The topic already exists on GitHub and is gradually being adopted, but it currently has no logo, description, or official links, which makes discoverability poor. Curating it will give the thousands of users and potential contributors an immediately recognizable, professional topic page with correct branding, a clear description, and links to the official website and repository.

Related existing topics this fits well with: productivity, todo, time-tracking, pomodoro, task-management, electron, angular, jira, github-issues.

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.

[jmeridth]

@Mustache-Games thank you for your contribution. Got some test failures to address. Once done, I'm good merging this.