clippy: fix first doc comment paragraph is too long

warning: first doc comment paragraph is too long
   --> src/lib.rs:729:1
    |
729 | / /// Similar to `kind`, but only reports the
730 | | /// [Cargo crate types](https://doc.rust-lang.org/cargo/reference/cargo-targets.html#the-crate-type-field):
731 | | /// `bin`, `lib`, `rlib`, `dylib`, `cdylib`, `staticlib`, `proc-macro`.
732 | | /// Everything that's not a proc macro or a library of some kind is reported as "bin".
733 | | ///
734 | | /// Other possible values may be added in the future.
    | |_
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#too_long_first_doc_paragraph
    = note: `#[warn(clippy::too_long_first_doc_paragraph)]` on by default

src/lib.rs

@@ -728,6 +728,7 @@ impl fmt::Display for TargetKind {
 
 /// Similar to `kind`, but only reports the
 /// [Cargo crate types](https://doc.rust-lang.org/cargo/reference/cargo-targets.html#the-crate-type-field):
+///
 /// `bin`, `lib`, `rlib`, `dylib`, `cdylib`, `staticlib`, `proc-macro`.
 /// Everything that's not a proc macro or a library of some kind is reported as "bin".
 ///