📝 update readme with setup (#89)

Author: benkutil

Readme.md

@@ -1 +1,7 @@
-# Personal Website
+# Personal Website
+Personal website using [11ty](https://11ty.dev) and [Cloudflare Pages](https://pages.cloudflare.com). I've tagged previous versions of the website as [releases](https://github.com/benkutil/benkutil.github.io/releases).
+
+## Setup
+### Environment variables
+- `ELEVENTY_ENV` is either `production` or `preview`. Defaults to not set.
+- In Cloudflare Pages, set `NODE_VERSION` to desired nodejs version. Currently set to `16.18` to match GitHub Codespace version.