Add Laravel 8 Support

[jasminetracey]

When I try to install on a laravel 8 project I get

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires markwalet/laravel-changelog ^1.4 -> satisfiable by markwalet/laravel-changelog[v1.4.0].
    - markwalet/laravel-changelog v1.4.0 requires illuminate/console 6.*|7.* -> found illuminate/console[v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev] but these were not loaded, likely because it conflicts with another require.