Manually create a 404 page. Fixes #12

Svelte Kit doesn't offer a good way to generate single HTML pages like 404.html, so I have to generate a regular page and then move it. Solution suggested here: sveltejs/kit#1209 (comment)

package.json

@@ -5,9 +5,11 @@
   "scripts": {
     "dev": "svelte-kit dev",
     "build": "npm run clean && svelte-kit build",
+    "build:sitemap": "svelte-sitemap --domain https://cuibonobo.com",
+    "build:404": "ncp ./build/404/index.html ./build/404.html && rimraf ./build/404",
     "clean": "rimraf ./build",
     "clean:all": "npm run clean && rimraf ./svelte-kit",
-    "postbuild": "svelte-sitemap --domain https://cuibonobo.com",
+    "postbuild": "npm run build:sitemap && npm run build:404",
     "preview": "svelte-kit preview",
     "check": "svelte-check --tsconfig ./tsconfig.json",
     "check:watch": "svelte-check --tsconfig ./tsconfig.json --watch",
@@ -40,6 +42,7 @@
     "gray-matter": "^4.0.3",
     "marked": "^2.1.3",
     "moment": "^2.29.1",
+    "ncp": "^2.0.0",
     "node-glob": "^1.2.0",
     "postcss": "^8.3.6",
     "prettier": "^2.3.2",

src/routes/404.svelte

@@ -0,0 +1,10 @@
+<script lang="ts">
+  import Title from '../components/Title.svelte';
+</script>
+
+<Title title="404: Not Found!" />
+<p>
+  <a href="https://en.wikipedia.org/wiki/Link_rot">Link rot</a>] is a serious problem on the
+  internet and I'm sorry to have contributed to it. Hopefully you'll find what you're looking for by
+  using the navigation links above.
+</p>