feat: Set up Eleventy and restructure project

Install and configure Eleventy for static site generation.

- Reorganized project directories for Eleventy conventions.
- Created base.njk, header.html, and footer.html for modularity.
- Wrote the initial landing page content in index.njk.

,eleventy.js

@@ -0,0 +1,14 @@
+module.exports = function (eleventyConfig) {
+  // Pass through static assets without processing
+  eleventyConfig.addPassthroughCopy("src/images");
+  eleventyConfig.addPassthroughCopy("src/styles");
+  eleventyConfig.addPassthroughCopy("src/scripts");
+
+  return {
+    dir: {
+      input: "src",
+      output: "_site",
+      includes: "includes",
+    },
+  };
+};