add README

README.md

+# io_uring faulty cancel reproducer
+
+Reproducer for the rpoblem reported here:
+https://lore.kernel.org/io-uring/21588bc9-592c-7793-c72a-498ba0db4937@kernel.dk/T/#t
+
+## Building
+
+The io_uring-cancel reproducer can be build using make  
+
+`$ make`
+
+or using meson  
+
+`$ meson build --buildtype=release && ninja -C build`
+
+When using make liburing >= 2.0 must be installed.
+
+## Running
+
+`io_uring-cancel [write_increment=0]`