Address review feedback on draft PR guidelines formatting and content

[Copilot]

Addresses review comments from merks and HeikoKlare on draft PR guidelines in CONTRIBUTING.md.

Changes

• Markdown formatting: New sentences within bullet points now start on new lines with proper indentation (2 spaces), improving readability and following markdown conventions
• Style cleanup: Removed unnecessary italics from e.g.
• Enhanced guidance: Added note that PR creators should explicitly state what feedback they seek in the description, since draft PRs may be overlooked otherwise

Example

Before:

- A shield against comments or reviews. Marking a PR as draft does not mean "leave me alone" – it means you welcome early feedback and collaboration.

After:

- A shield against comments or reviews.
  Marking a PR as draft does not mean "leave me alone" – it means you welcome early feedback and collaboration.

The feedback guidance addition:

- You are **seeking early feedback** from the community on your approach, design decisions, or implementation.
  **Important:** Clearly state in the PR description what kind of feedback you are seeking, as draft PRs may be overlooked until marked as ready for review.

Original prompt

Please address review comment from merks and HeikoKlare here eclipse-platform#260

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