Update to PureScript v0.15.0

[sigma-andex]

Description of the change

Backlinking to purescript/purescript#4244

Migrates FFI to ES modules

---

Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)

[sigma-andex]

🏓 @JordanMartinez

[thomashoneyman]

Let's hold off merging until we make a decision wrt which Node version to support and whether we'll allow arrow functions.

[JordanMartinez]

Need a changelog entry update here, too.

[JordanMartinez]

Shouldn't this be

return to => {
  return () => {
  };
];