21056 auto install document (#21362)

#21056

Document for policy-based automatic software installation.
See result
[here](https://github.com/fleetdm/fleet/blob/21056_auto_instal_document/articles/automatic-software-install-in-fleet.md#add-policy)

---------

Co-authored-by: spokanemac <jack@jdstrong.com>
Co-authored-by: Noah Talerman <noahtal@umich.edu>
Co-authored-by: JD <spokanemac@users.noreply.github.com>
Co-authored-by: Luke Heath <luke@fleetdm.com>

website/config/routes.js

@@ -570,6 +570,7 @@ module.exports.routes = {
   'GET /learn-more-about/apple-business-manager-teams-api': 'https://github.com/fleetdm/fleet/blob/main/docs/Contributing/API-for-contributors.md#update-abm-tokens-teams',
   'GET /learn-more-about/apple-business-manager-gitops': '/docs/using-fleet/gitops#apple-business-manager',
   'GET /learn-more-about/s3-bootstrap-package': '/docs/configuration/fleet-server-configuration#s-3-software-installers-bucket',
+  'GET /learn-more-about/policy-automation-install-software': '/guides/automatic-software-install-in-fleet',
   'GET /learn-more-about/exe-install-scripts': '/guides/exe-install-scripts',
   'GET /learn-more-about/install-scripts': '/guides/deploy-software-packages#install-script',
   'GET /learn-more-about/uninstall-scripts': '/guides/deploy-software-packages#uninstall-script',