doctl-databases-*: add page (#10882)

* doctl-databases-*: add page

---------

Co-authored-by: Reinhart Previano Koentjoro <reinhart_previano@yahoo.com>
Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/doctl-databases-firewalls.md

@@ -0,0 +1,20 @@
+# doctl databases firewalls
+
+> Manage firewalls for database clusters.
+> More information: <https://docs.digitalocean.com/reference/doctl/reference/databases/firewalls>.
+
+- Run a `doctl databases firewalls` command with an access token:
+
+`doctl databases firewalls {{command}} --access-token {{access_token}}`
+
+- Retrieve a list of firewall rules for a given database:
+
+`doctl databases firewalls list`
+
+- Add a database firewall rule to a given database:
+
+`doctl databases firewalls append {{database_id}} --rule {{droplet|k8s|ip_addr|tag|app}}:{{value}}`
+
+- Remove a firewall rule for a given database:
+
+`doctl databases firewalls remove {{database_id}} {{rule_uuid}}`