[Feature] migrate to bootstrap 4

[tim-hub]

The stable version 4 is released, I think it is a good time to migrate to bootstarp 4.

[amranidev]

Yes I'm planning for that

[Muhammadinaam]

Hi, this is a nice package but I think that the developers have stopped working on it. Maybe you can try this package: https://github.com/Muhammadinaam/speed-admin. It supports Laravel 8+.