Closes #159 preserve_pr_websites: keep files on gh-pages

[bundfussr]

Pull Request

Use keep_files: true to avoid that existing files on the gh-pages branch are removed when the website is build and deployed.

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By default, a temporary website with the content of the PR is created. To avoid this add [skip website] to the title of the PR.

[github-actions]

The website is available at https://pharmaverse.github.io/examples/159_preserve_pr_websites.

[bundfussr]

Hi @pawelru , why is the website built and deployed every day?

Should we add a comment here why it is necessary?

[pawelru]

good question - I don't quite remember the rationale to be honest. Happy to change and make it more rarely

[bundfussr]

OK, I've removed the schedule event.