Clarify that contributions are meant to be positive, and add a short intro to point out that the expectations placed upon contributors sections exist.

[rikkimax]

This was talked about at the monthly meeting yesterday, It was agreed that a sentence saying that we want human contributions, not automated tools ruling the PR queue. Basically, a friendly way of saying an LLM is a tool, anything it produces must be intended to go in by a human, rather than the tool making the decisions for a human without understanding it.

To kick this off, I'll give @mdparker and @LightBender a ping, to see how far off this is.

[dlang-bot]

Thanks for your pull request and interest in making D better, @rikkimax! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#21364"

[jmh530]

Item 4 is in a list of things that will not be viewed with favor. So it's not really written consistently with the others. How about something like:
"Contributors who do not understand the code they are contributing. If the contributor does not understand the code they are contributing, how can reviewers or other members of the community be expected to? A contribution is a representation of the contributor's desire to solve a problem. Any contribution should be done with intent and understanding."

[rikkimax]

I like the text related to understanding, but not the statement as a whole, needs to be thought about.