Add alerts

[GuillaumeGomez]

It'd be interesting to be able to add alerts on something like cpu or memory usage like this:

• add a dropdown to select component
• add a dropdown to select at which value we want to raise the alert
• the time being at this value before sending the alert

Of course, these alerts would be stored in local storage (so nothing server side). And for the alert, I was just thinking about changing the favicon by adding something onto it (we should add a favicon btw) and maybe a sound?