yarn init allows invalid package name

[KonradLinkowski]

Do you want to request a feature or report a bug?
Bug report

What is the current behavior?
yarn init allows package name to be in camelCase.
If the current behavior is a bug, please provide the steps to reproduce.

What is the expected behavior?
Package name should not contain uppercase letters.
Package name should match regex:
^(?:@[a-z0-9-~][a-z0-9-._~]*/)?[a-z0-9-~][a-z0-9-._~]*$
Please mention your node.js, yarn and operating system version.

• node.js: v10.14.1
• yarn 1.17.3
• operating system: Windows 10