PVF: Add missing crate descriptions (#7587)

polkadot/node/core/pvf/common/Cargo.toml

@@ -1,5 +1,6 @@
 [package]
 name = "polkadot-node-core-pvf-common"
+description = "Polkadot crate that contains functionality related to PVFs that is shared by the PVF host and the PVF workers."
 version.workspace = true
 authors.workspace = true
 edition.workspace = true

polkadot/node/core/pvf/common/src/lib.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-//! Functionality that is shared by the host and the workers.
+//! Contains functionality related to PVFs that is shared by the PVF host and the PVF workers.
 
 pub mod error;
 pub mod execute;