### What?
Updates create-next-app's templates' `.gitignore` files for parity with
[Yarn's official
recommendations](https://v3.yarnpkg.com/getting-started/qa#which-files-should-be-gitignored),
accounting for Yarn's modern Plug-n-Play functionality.
Fixes#65586
### Why?
New projects initialized with create-next-app presently add various
extraneous files from the Yarn cache to the initial commit. This is most
notable in the case of the Next SWC binary, which may exceed 100M in
some environments and prevent users from pushing their new projects to
free GitHub repositories without rewriting the commit history or setting
up Git LFS.
### How?
I've opted to follow the recommendations for
non-[Zero-Install](https://yarnpkg.com/features/caching#zero-installs)
configurations as Zero-Install may necessitate additional configuration
and present additional complications for unsuspecting users, so I think
it's best left up to the user to opt-in.
Contrary to the example `.gitignore`s provided by Yarn, I've excluded
the `.yarn/sdks` directory as it contains IDE-specific tooling which I
think is also best left up to the user to opt-in to including.
I have retained the current `.gitignore`'s exclusion of the `/.pnp`
directory for backwards compatibility with older versions of Yarn.
b3d9098383