build(deps): bump pixi.js from 6.5.1 to 8.15.0 in /small-angle-demo

Bumps [pixi.js](https://github.com/pixijs/pixijs) from 6.5.1 to 8.15.0.
- [Release notes](https://github.com/pixijs/pixijs/releases)
- [Commits](pixijs/pixijs@v6.5.1...v8.15.0)

---
updated-dependencies:
- dependency-name: pixi.js
  dependency-version: 8.15.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]