Add y-axis label markers to help people understand the visualisation

[mhansen]

I'm trying to popularise these visualisations for mobile development, but common feedback I get is that people aren't sure what they're looking at.

I think adding axis labels would help.

Just something like +100ms, +200ms, along the left side of the vis, would help I think to make it clear that the cells represent subsecond slices.

What do you think? We could possibly work on this. Wondering if you think this would be a reasonable addition.

[mhansen]

Here's a very rough mock-up (in macOS Preview) of what i'm thinking. Maybe with more markers.

[mhansen]

As extra benefit, it'd remind me which way time goes. I can't remember if time goes up or down in these graphs. I might have got the above the wrong way around!