traffic_top doc should explain output

The current traffic_top page
https://docs.trafficserver.apache.org/en/latest/appendices/command-line/traffic_top.en.html
contains just the cli option (#seconds to refresh). It doesn't explain any of the output.

Would be nice to describe each of the line items. For instance, under the Cache info column, what does Fresh mean (contrasting with Revalidate, Cold, Changed)... and then what are the same in ms.

Probably could start with a screen shot and describe the mini-sections (like status Code 'histogram' in the upper right; followed by 'histogram' of file sizes).