Add missing period in creating-gists#about-gists

[nguyenalex836]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/get-started/writing-on-github/editing-and-sharing-content-with-gists/creating-gists#about-gists

What part(s) of the article would you like to see updated?

public gists show up in Discover, where people can browse new gists as they're created.

Capitalize the first letter in this sentence

Additional information

No response