Pull request guide: mention to target our repositories

[a2937]

I believe we ought to mention somewhere that they need to open a pull request to https://github.com/freeCodeCamp/freeCodeCamp instead of https://github.com/<Your Github Username>/freeCodeCamp. I just spotted two PRs by a first-time contributor that we will never actually be able to merge because it affects their fork.

[gikf]

Does Proposing a Pull Request section counts? https://contribute.freecodecamp.org/how-to-open-a-pull-request/#proposing-a-pull-request

[a2937]

By default, all pull requests should be against the freeCodeCamp main repo, main branch.

Make sure that your Base Fork is set to freeCodeCamp/freeCodeCamp when raising a Pull Request.

I see what you mean. But I feel like we need a flashy warning sign nearby it.

[gikf]

Second sentence could be changed into callout. But since note about this is also in the checklist, I'm not sure it will help.