v1.13.0

This release updates to Buildroot
2020.08 and OTP 23.1.1.

• Updated dependencies

  • nerves_system_br: bump to v1.13.2
  • Erlang/OTP 23.1.1
  • erlinit 1.8.0
  • nerves 1.7.0

• New features

  • Added support for updating the root filesystem using firmware patches.
    See the [firmware patch docs](https://hexdocs.pm/nerves/experimental-features.html