fix issues-40 & add improvements in default chart styles

[ArielMejiaDev]

It fixes this issues:

• The stubs and commands are published by the service provider each time the application is started
• It should be only published on vendor:publish. No every time.
• It will break on anything hosted on serverless (by publishing files on every request).

reference here: https://github.com/ArielMejiaDev/larapex-charts/issues/40