Add instructions about splitting header and runtime + run_export> packages

[hmaarrfk]

PR Checklist:

• [ ] note any issues closed by this PR with closing keywords
• [ ] if you are adding a new page under docs/ or community/, you have added it to the sidebar in the corresponding _sidebar.json file
• [ ] put any other relevant information below

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[jaimergp]

pre-commit.ci autofix