Updates to Streaming Timeseries

[maximlt]

The example had to be merged quite quickly without having enough time to add a few improvements listed in the review:

For future extensions to this example (not this PR):

• add event detection
• add memory load in side plot for cpu stream
• add image stream with pos estimation in additional side plot
• add copy-pastable app at bottom

Originally posted by @droumis in #469 (comment)

[maximlt]

There was also:

• Get the main app to stream some data for a little while building the site, the objective being to run some more code so the notebook is more tested on the infrastructure, and possibly replace the existing screenshot by the real app. See Streaming Timeseries example #469 (comment)
• The app has a notebook flag to declare whether it should be displayed in a template or not:
  • Isn't there a way to automatically detect the context? See Streaming Timeseries example #469 (comment)
  • The app uses two variables, layout and template, that it returns conditionally in __panel__(). In theory it could just have one (e.g. view) but apparently something odd was going on and needed more investigation, see Streaming Timeseries example #469 (comment)

[droumis]

Also,

• "Return to Stream Follow" needs to be investigated, as it's not working with the current implementation. It should be that "Zooming or panning temporarily pauses the viewport’s displayed range; clicking ‘reset’ restores the viewport range to follow the latest stream updates."
• Use of pn.io.unlocked could use the some eyes from a senior engineer