Filtering possibilities

Hey Felix,

Thank you so much for this tool, it is so handy!

Currently, I'm trying to overcome a problem of `go tool trace` visualizer for user-defined tasks and regions, which is sometimes too slow (and the browser can't process it). We had an idea to filter out everything but tasks and regions, so there is fewer data to visualize.

Based on your tool, I was trying to come up with some "filtering" and leave as fewer events as possible - https://github.com/rumyantseva/traceutils/blob/filter/cmd/traceutils/filter.go & https://github.com/rumyantseva/traceutils/blob/filter/pkg/filter/filter.go. My current approach is too naive as things like `encoding.EventString` need to be handled more carefully, and there are some other hierarchical events that need proper handling.

So, I'm trying to find some documentation or articles to understand the relations between different events, but it doesn't seem to be super straightforward. If you have a moment, could you recommend some sources to learn from, please?

Thank you!