Update external URL references to point to ddev/ddev-intellij-plugin

[rfay]

Is there an existing issue for this?

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Are you sure that this bug is related to this DDEV Integration Plugin?

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Describe the bug

There are a number of external references to the php-perfect URL:

• [ ] DDEV docs (ddev/ddev)
• [ ] ddev.com (probably) (ddev/ddev.com)
• [ ] Jetbrains plugin page

GitHub does a phenomenal job of redirects, but we certainly want the correct URLs everywhere.

Steps to reproduce

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Additional context

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