Update README.md

[NickBusey]

Current command example fails with error Error: required flag(s) "pkg-name" not set

This fixes that, as well as fixing the package name to be consistent with the name lower down in the instructions.

[CLAassistant]

All committers have signed the CLA.

[Ghostwritten]

I thought it was my fault

[Ghostwritten]

Current command example fails with error Error: required flag(s) "pkg-name" not set

This fixes that, as well as fixing the package name to be consistent with the name lower down in the instructions.

how long?

[jharshman]

Bit of context: #817.
For completeness, you should include the following notes:

For adding commands, you should be inside your project root.
Init will no longer fail on non-empty directories.

[jharshman]

covered by #904