Build fails with vendored dependencies

[v-morlock]

Hi, due to the use of the "document features" crate, this crate won't build when vendoring dependencies. (slint-ui/document-features#20)

Would it be possible to place this behind a feature flag or sth similar to make building with vendored dependencies possible? That's relevant eg when packaging for nix.

error: Could not find documented features in Cargo.toml
  --> /private/tmp/nix-build-rerun-cli.drv-0/rerun-cli-vendor.tar.gz/ehttp/src/lib.rs:21:10
   |
21 | #![doc = document_features::document_features!()]
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |

[v-morlock]

My bad, this already works in the latest published version