Adds an alert for changes to the story

[johnarban]

This adds a simple alert to inform users about changes to the story. In it's current presentation it is added/removed manually. But we could add a built in time limit (like only show for 7 days).

This will be useful to have once we the larger changes to how we display current events, or if we add features (like anciliary data layers, or links out to that days data on earthdata, etc)

[patudom]

A few thoughts on this:

• Can you please put the snackbar in the upper right of the screen, near the button? Contextually, it feels like it wants to be associated with the button.
• I think we want to separate general user interface updates (like the new lat/long URL in Save map and time state in URL #89) from detailed science updates that maynot be meaningful to the general user (like the update to how the data are processed).
• I think we do need to have a popup somewhere that describes how the data are processed, and changes like that can go in some history there.
• Should the popup box link to a longer historical "change log"?
• Should the SnackbarAlert be a component in the vue-toolkit repo instead of here?
• On my phone, the button overlaps the title. It probably should go below the title?
  

[johnarban]

Closing this as it's changes have been merged into #89