Update to Laravel 8 (#127)

Adding support for Laravel 8.*

Code improvements (#110)

* Finishing styleci configuration

* adding php-cs-fixer with custom configuration

- Minor bugfixes related to changes on the sweet alert 2 js api.

- New changelog file.
- Facade dockblocks for ide intellisense.

- Bugfix related to persistent alert confirm button.

- Upgraded to the new sweetalert js api according to [THIS](https://s…

…weetalert.js.org/guides/#upgrading-from-1x) migration guide from 1.x to 2.0.

- Only supports `PHP >= 7.0`.
- Added method `addButton` to create new custom buttons.
- Added method `setConfig` to customize the configuration "by hand".

1.4.2

- Added package discovery for Laravel 5.5
- Middleware class name type fixed.

Merge pull request #48 from uxweb/develop

Fix readme typos

1.4.0

- Cancel button config added.
- Documentation improvements.