feat: Add NGINX Ingress Controller landing page (#929)

This commit adds a custom landing page for NGINX Ingress Controller
using a relatively new landing page archetype. The landing page is
intended to give an impression of the product and provide links to some
of the more commonly visited pages of both new and returning readers.

The addition of these landing pages is a requirement for the new
documentation theme's release, which receives ongoing updates.

Author: ADubhlaoich

content/nic/_index.md

@@ -1,6 +1,41 @@
 ---
+# The title is the product name
 title: NGINX Ingress Controller
+# The URL is the base of the deployed path, becoming "docs.nginx.com/<url>/<other-pages>"
 url: /nginx-ingress-controller/
+# The cascade directive applies its nested parameters down the page tree until overwritten
 cascade:
+  # The logo file is resolved from the theme, in the folder /static/images/icons/
   logo: NGINX-Ingress-Controller-product-icon.svg
+# The subtitle displays directly underneath the heading of a given page
+nd-subtitle: 
+# Indicates that this is a custom landing page
+nd-landing-page: true
+# Types have a 1:1 relationship with Hugo archetypes, so you shouldn't need to change this
+nd-content-type: landing-page
+# Intended for internal catalogue and search, case sensitive:
+# Agent, N4Azure, NIC, NIM, NGF, NAP-DOS, NAP-WAF, NGINX One, NGINX+, Solutions, Unit
+nd-product: NIC
 ---
+
+## About
+
+NGINX Ingress Controller is an [Ingress Controller]({{< ref "/nic/glossary.md#ingress-controller">}}) implementation for NGINX that can load balance Websocket, gRPC, TCP and UDP applications. 
+
+It supports standard [Ingress]({{< ref "/nic/glossary.md#ingress">}}) features such as content-based routing and TLS/SSL termination. Several NGINX and NGINX Plus features are available as extensions to Ingress resources through [Annotations]({{< ref "/nic/configuration/ingress-resources/advanced-configuration-with-annotations">}}) and the [ConfigMap]({{< ref "/nic/configuration/global-configuration/configmap-resource">}}) resource.
+
+## Featured content
+
+{{<card-layout>}}
+  {{<card-section showAsCards="true" isFeaturedSection="true">}}
+    {{<card title="Install NGINX Ingress Controller with Helm" titleUrl="/nginx-ingress-controller/installation/installing-nic/installation-with-helm">}}
+      Use Helm to deploy and configure a NGINX Ingress Controller cluster
+    {{</card>}}
+    {{<card title="Migrate from Ingress-NGINX Controller" titleUrl="/nginx-ingress-controller/installation/ingress-nginx">}}
+      Replace an Ingress-NGINX cluster with NGINX Ingress Controller
+    {{</card>}}
+    {{<card title="Releases" titleUrl="/nginx-ingress-controller/releases">}}
+      Review the changes from the latest NGINX Ingress Controller releases
+    {{</card>}}
+  {{</card-section>}}
+{{</card-layout>}}