Fixes for file-watching, user assets, and system dependencies (#2)

* fix: avoid panics in case of non-existing path for watching

* fix: copy the themes and plugins

* Revert "add a few more libraries to the linux script"

This reverts commit 7509677003da3398d0df796eca9c5435a12f576e.

* fix: add vulkan validation layers to the system deps

* fix: fix the themes paths