docs need some polish love

[Fred Grott]

Hello,

I finally got it working by re-reading DCM docs to figure how to configure some of the lint rules as it is not in the docs...and also not in docs is how DCM structured the options command line arguments. Generally, you want this at the command line:

`dart run flutterando_metrics:metrics analyze lib --reporter=html --output-directory=reports/metrics

`

I appreciate the hard work the Flutterando group has done to rescue this neat tool.