Open OnDemand/OnDemand Loop as an external tool in the guides

[pdurbin]

We should add Open OnDemand/OnDemand Loop as an external tool in the guides on a future version of this page: https://guides.dataverse.org/en/6.7.1/admin/external-tools.html#inventory-of-external-tools

We've already added it to the demo server:

• To demo server, add external tool for Open OnDemand dataverse.harvard.edu#390

Parent issue:

• Project: Open OnDemand (OOD) and Dataverse Integration Proof-of-Concept dataverse-pm#338