Update license and about section to our template and samples README

[lydiasama]

Why

Most projects in Nimble's repository have the license and about sections to represent the copyright. So we should add it to our template and samples too.

Example template that includes this part:

• https://github.com/nimblehq/ios-templates
• https://github.com/nimblehq/gin-templates
• https://github.com/nimblehq/elixir-templates
• https://github.com/nimblehq/react-templates
• https://github.com/nimblehq/rails-templates

Who Benefits?

Project owner -- us. 🙌🏻

[toby-thanathip]

Resolved in #280