message: add `cargo-features` to unstable docs for workspace inheritance
diff: @@ -1256,6 +1256,8 @@ documentation = "https://example.github.io/example"
  ```toml
  # [PROGECT_DIR]/bar/Cargo.toml
  +cargo-features = ["workspace-inheritance"]
  +
  [package]
  name = "bar"
  version.workspace = true
  @@ -1290,6 +1292,8 @@ dep-dev = "0.5.2"
  ```toml
  # [PROGECT_DIR]/bar/Cargo.toml
  +cargo-features = ["workspace-inheritance"]
  +
  [project]
  name = "bar"
  version = "0.2.0"
  