Add a button to create a role in the roles tab

https://www.figma.com/proto/h2HxCPmleg9x1IMfPbCJrd/Infinispan?page-id=132%3A13700&node-id=212-24998&viewport=369%2C117%2C0.15&scaling=scale-down&starting-point-node-id=167%3A21894

This will open a modal to create a role (follow the link to see all)

https://www.figma.com/proto/h2HxCPmleg9x1IMfPbCJrd/Infinispan?page-id=132%3A13700&node-id=249-24919&viewport=369%2C117%2C0.15&scaling=scale-down&starting-point-node-id=167%3A21894

Once the role is created, an alert is displayed and the list is refreshed.

https://www.figma.com/proto/h2HxCPmleg9x1IMfPbCJrd/Infinispan?page-id=132%3A13700&node-id=249-27387&viewport=369%2C117%2C0.15&scaling=scale-down&starting-point-node-id=167%3A21894

The REST API to create a role exists, but needs a modification to support adding descriptions. Issue to be linked. On top of that, the documentation of the REST API is missing.