add export default p5 at end of global.d.ts

[nbogie]

Resolves #8302

Changes:
adds a final export default p5 to global.d.ts when it's prepared in typescript.mjs

changes one of the type tests (test/types/basic.js) to use this default import.

Prepared following @davepagurek 's instruction. (Thanks!)

PR Checklist

• npm run lint passes
• Unit tests are included / updated

[nbogie]

Also tested the fix successfully with a couple of p5 global-mode typescript projects, locally, including this non-trivial one.

Process:

used npm pack on the patched p5 code, and and
then in my test projects ran npm install that-new-p5.tgz in place of p5 from npm.
Changed those projects to use import p5 from "p5/global".
Both type-checked and ran fine.