Incorrect README.md commands for yarn

[iffa]

I'm submitting a...

[ ] Regression 
[x] Bug report
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

Creating a new project using nest new and selecting yarn as package manager incorrectly populates README.md with npm commands.

Expected behavior

nest new with yarn should populate README.md with yarn commands.

Minimal reproduction of the problem with instructions

nest new asd -p yarn

Environment

$ nest -V: 6.11.3