Feature request: A new graph used to display event markers

[clwgh]

Hello, thankyou for your continued work on this project.

This is a feature request for a new graph to display event markers and a button to add them.

This would be useful to note changes to the site. For example if a filter was installed, an event marker could be added so that this point in time is easy to find in future when looking at the graphs. This is especially useful with all_large=yes.

Here is a mock-up of how this might look.

Thankyou.