Add note for alpm being send

Morganamilo · Morganamilo · commit 70a793a4d807 · 2021-12-08T22:52:08.000Z
diff --git a/alpm/src/alpm.rs b/alpm/src/alpm.rs
@@ -24,6 +24,7 @@ impl std::fmt::Debug for Alpm {
     }
 }
 
+// TODO unsound: remove
 unsafe impl Send for Alpm {}
 
 impl Drop for Alpm {
