remove emabssy pro page and implement 404 page

.eleventy.js

@@ -4,6 +4,10 @@ const pluginSEO = require("eleventy-plugin-seo");
 const tinysvg = require('@sardine/eleventy-plugin-tinysvg');
 const slinkity = require('slinkity')
 
+// for 404 callback
+const fs = require("fs");
+const NOT_FOUND_PATH = "_site/404.html";
+
 module.exports = function (eleventyConfig) {
   eleventyConfig.addPassthroughCopy('./src/assets/images/');
   eleventyConfig.addPassthroughCopy('./src/assets/videos/');
@@ -22,6 +26,27 @@ module.exports = function (eleventyConfig) {
     return format(date, dateFormat)
   })
 
+  // 404 callback
+  eleventyConfig.setBrowserSyncConfig({
+    callbacks: {
+      ready: function(err, bs) {
+
+        bs.addMiddleware("*", (req, res) => {
+          if (!fs.existsSync(NOT_FOUND_PATH)) {
+            throw new Error(`Expected a \`${NOT_FOUND_PATH}\` file but could not find one. Did you create a 404.html template?`);
+          }
+
+          const content_404 = fs.readFileSync(NOT_FOUND_PATH);
+          // Add 404 http status code in request header.
+          res.writeHead(404, { "Content-Type": "text/html; charset=UTF-8" });
+          // Provides the 404 content without redirect.
+          res.write(content_404);
+          res.end();
+        });
+      }
+    }
+  });
+
   return {
     dir: { input: "src", output: "_site", data: "_data" },
   };