Update CONTRIBUTING.md links and add Discord invitation

- Update contributor docs link to https://p5js.org/contribute/
- Update community statement link to https://p5js.org/about/#community-statement
- Add Discord server link with #contribute-to-p5 channel mention

Fixes #6929

Author: RishiAhuja

CONTRIBUTING.md

@@ -1,10 +1,10 @@
 Hi there! Welcome to p5.js contributing! Here are a few things to know:
 
-The GitHub issues are for bugs and feature requests for the p5.js library itself. If you have a general question or bug programming with p5.js please post it in the [p5.js forum](https://discourse.processing.org/c/p5js).
+The GitHub issues are for bugs and feature requests for the p5.js library itself. If you have a general question or bug programming with p5.js please post it in the [p5.js forum](https://discourse.processing.org/c/p5js) or ask in our [Discord server](https://discord.gg/SHQ8dH25r9) (check the #contribute-to-p5 channel).
 
 Please make sure you are posting to the correct repository. See this [section](https://github.com/processing/p5.js/blob/main/README.md#issues) for a list of all p5.js repositories.
 
-Please be sure to review our [community statement and code of conduct](https://github.com/processing/p5.js/blob/main/CODE_OF_CONDUCT.md). These things are very important to us.
+Please be sure to review our [community statement](https://p5js.org/about/#community-statement) and [code of conduct](https://github.com/processing/p5.js/blob/main/CODE_OF_CONDUCT.md).
 
-Check out the [contributor docs](https://github.com/processing/p5.js/blob/main/contributor_docs/) for more in-depth details about contributing code, bug fixes, and documentation.
+Check out the [contributor docs](https://p5js.org/contribute/) for more in-depth details about contributing code, bug fixes, and documentation.