add README

README.md

+# Realtime Kernel for Ubuntu 18.4
+
+These are deb packages built for Ubuntu Bionic.
+
+Used Kernel sources:
+- kernel `linux-5.4.19-rt11_5.4.19-rt11.orig.tar.gz`
+- realtime patch `linux-5.4.19-rt11_5.4.19-rt11-1.diff.gz`
+
+Kernel config:
+- Preemption Model: Fully Preemptible Kernel (RT)
+