SEO Improvements (#983)

* [site,seo][xs]: add custom _document with lang prop, add description to meta tags, make title larger

* [site,seo][xs]: add apple touch icon, add alt props to images

* [site,seo][xs]: add icon to default seo

* [site,seo][s]: implement next-sitemap

* [site,seo][s]: review page titles

* Rebuild package-lock.json files

* Regenerate package-lock

site/package.json

@@ -6,6 +6,7 @@
     "dev": "npm run mddb && next dev",
     "build": "next build",
     "prebuild": "npm run mddb && node ./scripts/fix-symlinks.mjs",
+    "postbuild": "next-sitemap",
     "start": "next start",
     "mddb": "mddb content"
   },
@@ -52,6 +53,7 @@
   "devDependencies": {
     "@tailwindcss/typography": "^0.5.9",
     "autoprefixer": "^10.4.14",
+    "next-sitemap": "^4.1.8",
     "postcss": "^8.4.22",
     "prettier": "^2.8.7",
     "remark": "^14.0.2",