add coq README

README.txt

+This folder contains the Coq development for Iris.
+It uses a Coq library in lib/ by Sieczkowski et al. to solve the recursive domain equation (see the paper for a reference).
+
+This folder is organized as follows:
+* core_lang.v contains the axioms about the language
+* lang.v defines the threadpool reduction and derives some lemmas from core_lang.v
+* masks.v introduces some lemmas about masks
+* world_prop.v uses the aforementioned Coq library to construct the domain for Iris propositions
+* iris.v is the main file and contains the actual logic and the proof of the rules for view shifts and Hoare tiples
+
+Be aware that iris.v takes a long time to check and needs significant amounts of RAM!
+8GiB may be sufficient, but to be safe you should have 16GiB and give it around 2 to 3 hours.