Update to latest version of yarn

[markdboyd]

Is there any plan to update the version of yarn in the buildpack? The included version of yarn is 1.22.22 on the latest buildpack release, whereas the latest available release of yarn is 4.18.0

[pburkholder]

Looks like there have been previous attempts at this:

• feat: add yarn berry support #679
• Yarn V3 Support #694
• Updated yarn 1 to yarn berry #326

[HaymondM]

I might give this another go! I'll take a look at those previous PRs to get some context and see what's needed for Yarn 4.