♻️ Replace old Docs landing by the new one

[AntoLC]

Feature Request

We want to replace the Docs landing page by the new one: https://lasuite.numerique.gouv.fr/produits/docs

We don't want to do a simple redirect, we want to keep https://docs.numerique.gouv.fr/ url but pointing on this url https://lasuite.numerique.gouv.fr/produits/docs.

What is doing Grist:

{{- if .Values.redirectLanding.enabled }}
      {{ $host := .Values.ingress.host }}
      {{ $upstreamVhost := get .Values.ingress.annotations "nginx.ingress.kubernetes.io/upstream-vhost" }}
      {{ $realHost := $upstreamVhost | default $host }}
      location ~ ^/$ {
        if ($cookie_grist_core_status = 'S') {
          proxy_pass http://grist-home-wk;
          set $proxy_host {{ $realHost }};
        }
        if ($cookie_grist_core_status != 'S') {
          return 302 {{ .Values.redirectLanding.url }};
        }
      }
      {{- end }}