Add link to NOTICES in pyproject.toml

Author: ValerianRey

pyproject.toml

@@ -56,6 +56,9 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+This software includes third-party code. See the NOTICES file for the relevant
+copyright notices and license texts.
 """
 
 [project.urls]