Cargo Features

markup_fmt has no features set by default.

[dependencies]
markup_fmt = { version = "0.18.0", features = ["config_serde"] }
config_serde = serde

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

serde config_serde?