Suggestion for run --scope docs

[or-yam]

Expected Behavior

The documentation for the --scope flag in run command could be more clear and beginner-friendly.

Current Behavior

Documentation for the --scope flag is only available in filter options.
It might be difficult to understand it refers to the package name inside the package.json file.

Possible Solution

Explain in lerna/commands/run/README that the --scope flag accepts a package name from its package.json file.

Context

I tried using lerna run --scope and it took me a while to realize what value to use for this flag.

[or-yam]

If you would like to, I can make the improvements suggested above.