README: add good practices for forking, porting or rewriting VESC Tool

[RageMechanics]

As suggested on the VESC Discord, this adds the "good practices" summary for projects that fork, port or rewrite VESC Tool (e.g. in Rust, Flutter or for the web).

It is inserted right after the existing "Forks without branding" paragraphs; nothing else in the README is changed. It covers:

• GPL-3.0-or-later obligations for derivative works (notices, source, About screen, dependencies)
• Naming, logos, icons and visual identity under the trademark policy
• App identifiers, update checker and UI wording
• How to state compatibility, an About/credits template, distribution, and a short checklist

Feel free to edit or trim the wording directly.

[github-actions]

CLA Assistant Lite bot:
Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

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I have read the CLA Document and I hereby sign the CLA

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[RageMechanics]

I have read the CLA Document and I hereby sign the CLA