Cleanup root directory by moving the page files to pages

[wilzbach]

Ideally only the "Improve this page" link should change on the diff.

[dlang-bot]

Thanks for your pull request, @wilzbach!

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[CyberShadow]

This probably needs Andrei's sign-off, and he has historically been against moving things around under the hood...

[wilzbach]

This probably needs Andrei's sign-off, and he has historically been against moving things around under the hood...

Okay. I will refrain from fixing the CIs until then (shouldn't be too difficult).
My main motivation was that the root directory is so messy that e.g. on GitHub one has to scroll six pages (on my laptop) to reach the README.md. This is quite scaring and off-putting for new contributors.
(Git handles renames quite well and the history is preserved.)

[andralex]

Not a fan of this, and that "pages" is a generic uninformative name is a symptom. I'd go instead for a more logical cleanup, e.g. "ddoc", "articles", "scripts", "samples" etc.