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/pages/_app.tsx

@@ -47,7 +47,12 @@ function MyApp({ Component, pageProps }) {
       defaultTheme={siteConfig.theme.default}
       forcedTheme={siteConfig.theme.default ? null : 'light'}
     >
-      <DefaultSeo defaultTitle={siteConfig.title} {...siteConfig.nextSeo} />
+      <DefaultSeo
+        defaultTitle={siteConfig.title}
+        description={siteConfig.description}
+        titleTemplate="PortalJS - %s"
+        {...siteConfig.nextSeo}
+      />
 
       {/* Global Site Tag (gtag.js) - Google Analytics */}
       {siteConfig.analytics && (