Documentation: Update to VuePress v2

[Mastercuber]

For comfortable reasons it would be great to detect, and then refresh the page, history changes in the documentation.

Example: When I am here (Options) and go to here (Otpions#zoom) and then want back again to Options with the browser back button or a back button on the mouse, I still be at Options#zoom.

[kurkle]

We are using VuePress to serve the pages. I'm not good enough with it to know if this can be achieved.

[Mastercuber]

It seems like changing the vuepress version to version 2.x should be enough.

When I try what I described above on the vuepress 1.x docs site, it's not possible to jump around. But when I try it at the vuepress 2.x docs site, it's possible to do that.

And yeah, it's a beta version..

[kurkle]

Will look into upgrading, when there is a stable release of vuepress 2