docs: add gallery screenshot & link in README (#10988)

* docs: add gallery screenshot & link in README

* deallowing large files

.pre-commit-config.yaml

@@ -35,6 +35,7 @@ repos:
     rev: v3.2.0
     hooks:
       - id: check-docstring-first
+      - id: check-added-large-files
       - id: check-yaml
         exclude: ^helm/superset/templates/
       - id: debug-statements

README.md

@@ -48,6 +48,10 @@ A modern, enterprise-ready business intelligence web application.
 
 ## Screenshots & Gifs
 
+**Gallery**
+
+<kbd><a href="https://superset.apache.org/gallery"><img title="Gallery" src="https://raw.githubusercontent.com/apache/incubator-superset/master/superset-frontend/images/screenshots/gallery.png"></a></kbd><br/>
+
 **View Dashboards**
 
 <kbd><img title="View Dashboards" src="https://raw.githubusercontent.com/apache/incubator-superset/master/superset-frontend/images/screenshots/bank_dash.png"></kbd><br/>

docs/src/pages/404.jsx

@@ -25,7 +25,7 @@ const NotFoundPage = () => (
   <Layout>
     <SEO title="404: Not found" />
     <h1>NOT FOUND</h1>
-    <p>Sorry, you've requested a page that does not exist.</p>
+    <p>Sorry, you&apos;ve requested a page that does not exist.</p>
   </Layout>
 );