Use copilot-instructions.md as input for generating PR title/body

[EelcoLos]

Currently, see the commits and PR generate PR and use it often to just the the basics down. However, often they break the rules of my repo/organization.

I tried to replicate this at https://github.com/EelcoLos/nx-tinkering/blob/main/.github/copilot-instructions.md:

For a PR and commits: use semantic commit messages. For example, "feat: add a new feature" or "fix: correct a typo". Limit the first line to 72 characters or less. Use the body to explain what changes you have made and why you made them.

However, I don't see the generation integration when copilot-instructions.md is available, as it breaks the rules on the things i've instructed