added link for Preparing an Issue Guide at 2 places

[webermayank]

Fixes #3502

Changes: fixed broken link of Preparing an Issue in working-within-the-codebase and ideas-for-getting-started, added link to Preparing An Issue

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 #123

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[raclim]

Thanks so much for your work on this!

Since #3506 came in first, we decided to go with that one. I'm sorry that we couldn't get this one in, but please feel free to check out some of our other issues!

[webermayank]

No worries @raclim , i thought to ask you first before actually creating a PR thats why i left a comment in issue. It's good that the issue is now resolved.

[raclim]

@webermayank I'm so sorry I missed that comment! Thanks for noting this! If you'd like another issue that I think could be great and is similar to this one here, adding links to the release pages for the p5.js library and p5.js editor!

[webermayank]

Sure @raclim that would be great, Thankyou.