docs(site): new landing page for ekalinin.github.io/nodeenv

[ekalinin]

What happens

ekalinin.github.io/nodeenv is still the page GitHub's automatic page generator produced in 2013 from the gh-pages branch. It is a copy of the README at nodeenv 0.6.5: node v0.4.6, sudo easy_install, zip downloads of master, and a Universal Analytics tracker that stopped collecting in 2023. Nothing kept it in sync with the README, so it never moved.

What changes

• site/index.html and site/style.css: a single landing page. It has the install command, a quick start with the Windows activate scripts, three feature cards, the prebuilt/mirror/system options, a ~/.nodeenvrc sample, and links into the README for everything else.
• Every sentence restates README.rst. The page states no nodeenv, node or npm version, and the current release shows through the PyPI badge. So a release does not need a site edit.
• No JavaScript and no analytics. The only outside requests are the three badge images.
• Light by default and dark when the system prefers it. Prompts are not selectable, so copying a command block copies only the commands.
• .github/workflows/pages.yml: deploys site/ as is with the official Pages actions. It runs on master pushes that touch site/ or the workflow, and on manual dispatch.

After merge

The repository still serves Pages from the gh-pages branch, so the run triggered by the merge fails until the source is switched:

1. Settings, Pages: set the source to "GitHub Actions".
2. Run the Pages workflow by hand and check https://ekalinin.github.io/nodeenv/.
3. Tick "Enforce HTTPS" and change the repository homepage to https://ekalinin.github.io/nodeenv/.
4. Delete the gh-pages branch.

Until step 4, setting the source back to the branch restores the old page.

Checked

• Rendered in Chrome at 1280, 375 and 300 px, light and dark. At 375 px the cards stack and nothing overflows; at 300 px the two longest command blocks scroll inside themselves.
• With images blocked the badges fall back to their alt text.
• A network log of the page shows only the three badge requests.
• actionlint passes on the workflow, and the sdist built from this branch contains no site/ files.
• The README anchors #usage, #command-line-options and #configuration exist, and every link on the page returns 200.