Add Azure details

for example:
- how to see the limit of CPUs/MEM for a given node pool (check the zone - e.g. eastus - in the Nodes section of the pool), then in azure sponsorship section -> settings -> resources. It is possible to ask the support to increase this limit, I did for Switzerland North region.

## important: the azure service principal (internal account needed by azure) expires after 1 year
the service principal need to be renewed, following :
- az ad sp create-for-rbac --role Contributor --scopes /subscriptions/a2b00ada-7fb9-4e4f-8648-03f83044441a/resourceGroups/aiidalab-demo-server
- az aks update-credentials --resource-group aiidalab-demo-server --name demo-server-production --service-principal appId --client-secret password