refactor(scrollbar): experimental prefix over feature

A feature flag has quite some complexity with it and is annyoing.
Write a rustdoc comment about it and be clear about it being experimental and include it as is.

.github/workflows/rust.yml

@@ -40,7 +40,6 @@ jobs:
           - -D clippy::pedantic
         features:
           - "" # default features
-          - --all-features
         include:
           # Check future versions and maybe get some glances on soon to be lints
           - toolchain: beta