cmd/create: add vendor info to the metadata and change the author name parameter to required

[iawia002]

$ ksbuilder create

Please input extension name: aaa
✔ Performance
Please input extension author: ia
Please input Email (optional):
Please input author's URL (optional):
Directory: /xxx/aaa

The extension charts has been created.

ref https://github.com/kubesphere/issues/issues/1024 https://github.com/kubesphere/issues/issues/1097

/cc @wansir

[wansir]

LGTM