Add missing links to billing API (elastic#2282)

Author: shainaraskas

deploy-manage/cloud-organization/tools-and-apis.md

@@ -13,6 +13,8 @@ You can use the [{{ecloud}} API](https://www.elastic.co/docs/api/doc/cloud/) to
 * Refer to [](/deploy-manage/api-keys/elastic-cloud-api-keys.md) to learn how to generate an API key to access this API.
 * Refer to [{{ecloud}} RESTful API](cloud://reference/cloud-hosted/ec-api-restful.md) for usage information and examples.
 
+For additional billing and cost information for {{ecloud}}, you can use the [Cloud Billing API](https://www.elastic.co/docs/api/doc/cloud-billing/).
+
 For {{ecloud}} [service status](/deploy-manage/cloud-organization/service-status.md) updates, you can use the [Service Status API](https://status.elastic.co/api/).
 
 For information about all of the tools and APIs that you can use to manage your {{ech}} deployments and {{serverless-full}} projects, refer to [](/deploy-manage/deploy/elastic-cloud/tools-apis.md).

deploy-manage/deploy/elastic-cloud/tools-apis.md

@@ -33,6 +33,7 @@ The following REST APIs allow you to manage your {{ecloud}} organization, users,
 | {{ecloud}} organization<br><br>{{ech}} deployments | [{{ecloud}} API](https://www.elastic.co/docs/api/doc/cloud/) | Manage your Cloud organization, members, costs, billing, and more.<br><br>Manage your hosted deployments and all of the resources associated with them, including scaling or autoscaling resources, and managing network security, deployment extensions, remote clusters, and {{stack}} versions.<br><br>Refer to [{{ecloud}} RESTful API](cloud://reference/cloud-hosted/ec-api-restful.md) for usage information and examples. |
 | {{serverless-full}} projects | [{{serverless-full}} API](https://www.elastic.co/docs/api/doc/elastic-cloud-serverless) | Manage {{serverless-full}} projects. |
 | {{ecloud}} services | [Service Status API](https://status.elastic.co/api/) | Programmatically ingest [service status](/deploy-manage/cloud-organization/service-status.md) updates. |
+| {{ecloud}} billing information | [Cloud Billing API](https://www.elastic.co/docs/api/doc/cloud-billing/) | Retrieve additional billing and cost information about your {{ecloud}} organization. |
 
 
 ### APIs to interact with data and solution features