Feature/enhancement of hoverinig buttons

[haarsh157]

Fixes #2823, #2905

Changes:

1. Changed hovering color to p5jsActivePink.
2. Added new yellow color p5ContrastYellow and changed the button hovering color in the contrast theme.

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 #2823

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• p5.js-web-editor
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[raclim]

Thanks for your work on this!

I think overall this looks good! I made a few adjustments where I removed the changes to the RootPage.jsx file and the change to the foreground property in the theme.js file. I also feel that the p5jsActivePink color is not a noticeable enough difference to identify the hover state, but think that could be reconsidered down the line!