Add Undertale

[Drwhomust]

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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Curating a new topic or collection

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The Undertale community is big and there are many projects under this tag that provide assistance to making modifications to the orginal game. And also many open source fan projects that use undertale as a base concept. It would be nice for people to know info about the original game before they start digging into the projects under this tag.

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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.

[Drwhomust]

Wait that's my bad. Imma fix it

[Drwhomust]

Fixed it!
Sorry for the small bit of chaos