Added accesibility for default system theme to p5.js-web-editor

[takshittt]

I added a button in the settings dropdown menu as "system preferences" which enables default system theme of the user to the p5.js web editor.
Fixes #3061

Changes: added accessibility for default system theme in the p5.js-web-editor

I have verified that this pull request:

• [✔️ ] has no linting errors (npm run lint)
• [ ✔️] has no test errors (npm run test)
• [ ✔️] is from a uniquely-named feature branch and is up to date with the develop branch.
• [ ✔️] is descriptively named and links to an issue number, i.e. Fixes #3061

[yugalkaushik]

To check the checkbox you can add x between the square brackets.

[takshittt]

Reviewed and tested the implementation of the default system theme. Verified that theme switches correctly based on system preferences across supported browsers. Ready for review and merge.

[raclim]

Thanks so much for working on this!

I just checked it out and can confirm that it seems to work so far! I'm not sure if this might've been mentioned somewhere already, but could you delve into why react-helmet-async is added? Was it specifically for testing?

[takshittt]

The migration from react-helmet to react-helmet-async was primarily done for testing purposes, but not exclusively. It also helps maintain consistency between the testing and production environments. However, I realize this is a broader change that could affect the overall code workflow. I'm happy to switch back to react-helmet if you prefer.