Update contributing_to_the_p5js_reference for p5 v2#8462

nbogie wants to merge 1 commit intoprocessing:dev-2.0processing/p5.js:dev-2.0from

nbogie:fix-contrib-to-ref-guide-for-v2nbogie/p5.js:fix-contrib-to-ref-guide-for-v2Copy head branch name to clipboard