Add Pull Request template to improve contribution workflow

[hxrshxz]

Increasing Access

A pull request template helps new contributors know what details to include when they open a PR. It makes the process smoother for everyone and helps maintainers review changes faster. This also makes it easier for first-time contributors to get started and keeps PRs clear and consistent.

Most appropriate sub-area of p5.js?

Community

Feature request details

Right now, the repository doesn’t have a Pull Request template. Because of this:

• PR descriptions are often inconsistent
• Important details needed for reviews might be missing
• New contributors may not know what to include in their PRs