Reimagine uptime landing page when no index/data

[shahzad31]

Is your feature request related to a problem? Please describe.
When user lands on uptime in kibana, if they are using it first time/have no heartbeat configured, they see, simple error saying, "No Uptime index found".

Describe the solution you'd like
I think we should give user more info about uptime, probably by highlighting few features.
Something like

• With Uptime you can monitor your services/apps etc etc
• You can configure alerts directed to your Email/Slack when service goes down
• You can use Machine Learning to detect anomalies in your service response duration times.

[shahzad31]

We can get some inspiration from Graph and missing index pattern redesign being done in kibana elastic/kibana#57401

@katrin-freihofner @drewpost can we have design issue for this?