Feat: Add robots.txt to prevent demo site from being indexed

A robots.txt file has been added to the root of the site. It uses a blanket "Disallow: /" rule with an "Allow: /credits/" exception to ensure only the attributions page is indexed by search engines.

.eleventy.js

@@ -2,6 +2,7 @@ module.exports = function (eleventyConfig) {
     eleventyConfig.addPassthroughCopy({ "src/images": "images" });
     eleventyConfig.addPassthroughCopy({ "src/styles": "styles" });
     eleventyConfig.addPassthroughCopy({ "src/scripts": "scripts" });
+    eleventyConfig.addPassthroughCopy({ "src/robots.txt": "robots.txt"});
     return {
         dir: {
         input: "src",

src/robots.txt

@@ -0,0 +1,3 @@
+User-agent:*
+Disallow: /
+Allow: /credits/