Period should be automatically appended to project description (if missing)

[Reinmar]

... or we can explain it in the inquiry that "one sentence that ends with a period" :D

To test check:

> gulp create-package

[14:12:21] Starting 'create-package'...
? Enter package name without ckeditor5- prefix: x
? Enter application full name: x
? Enter package's initial version: 0.0.1
? Enter package's GitHub URL: ckeditor/ckeditor5-x
? Package description (one sentence):

Package description is then used in couple templates. In each of them it's expected that it ends with a period.