kernel: README: add a toc
Add Table Of Contents to the kernel README.md file.
+* [Build Kata Containers Kernel](#build-kata-containers-kernel)
+ * [Requirements](#requirements)
+ * [Setup kernel source code](#setup-kernel-source-code)
+* [Build the kernel](#build-the-kernel)
+ * [Install the Kernel in the default path for Kata](#install-the-kernel-in-the-default-path-for-kata)
+ * [Submit Kernel Changes](#submit-kernel-changes)
+ * [How is it tested](#how-is-it-tested)
+* [Contribute](#contribute)
+
+---
+
# Build Kata Containers Kernel
This document explains the steps to build a kernel recommended for use with
