Remove outdated resources

[Gamerboy59]

There appear to be unused and outdated resources (like bootstrap v5.1 or vue) in the public folder. I couldn't find where they're used since all new stuff with laravel-mix goes into app.js/.css etc. If these resources aren't used in this project, they should be deleted to not put outdated stuff on peoples webservers.
At the same time, the dev requirements in the package.json and composer.json should be reviewed in terms of necessity.

[Gamerboy59]

Outdated resources removed by commit 4dbfe6f.
Dev-Requirements review still necessarry.