Add note on concurrent reads

Author: Ipotrick

docs/taskgraph.md

@@ -78,6 +78,8 @@ Likely execution order generated by tg:
 
 Notice here that there are still dependencies formed to writes not marked as concurrent. So while B and C execute together, A and D form strong ordering dependencies to the concurrent writes.
 
+> NOTE: There is no extra concurrent read access, as all reads are implicitly concurrent already. Multiple reads will be sheduled independently to each other.
+
 ## Task
 
 The core part of any render graph is the nodes in the graph. In the case of Daxa, these nodes are called tasks.