chore: clarify location of prefab and di exceptions

lightbulb/exceptions.py

@@ -18,6 +18,12 @@
 # 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.
+"""
+Module containing exceptions raised by lightbulb internals. Exceptions raised by built-in hooks (prefab package)
+are instead kept within that package. See the ``lightbulb.prefab`` documentation page for their reference. Similarly,
+exceptions raised by the dependency injection system are contained in the ``lightbulb.di`` subpackage.
+"""
+
 from __future__ import annotations
 
 __all__ = [