kata-ctl: docs: Write basic documentation

Provide a basic document explaining a little about the `kata-ctl`
command.

Fixes: #5351.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

src/tools/kata-ctl/README.md

@@ -2,14 +2,48 @@
 
 ## Overview
 
+The `kata-ctl` tool is a rust rewrite of the
+[`kata-runtime`](../../runtime/cmd/kata-runtime)
+[utility program](../../../docs/design/architecture/README.md#utility-program).
+
+The program provides a number of utility commands for:
+
+- Using advanced Kata Containers features.
+- Problem determination and debugging.
+
 ## Audience and environment
 
-## History
+Users and administrators.
 
-## Full details
+## Build the tool
 
-## Code summary
+```bash
+$ make
+```
+
+## Install the tool
+
+```bash
+$ make install
+```
 
 ## Run the tool
 
-### Prerequisites
+```bash
+$ kata-ctl ...
+```
+
+For example, to determine if your system is capable of running Kata
+Containers, run:
+
+```bash
+$ kata-ctl check all
+```
+
+### Full details
+
+For a usage statement, run:
+
+```bash
+$ kata-ctl --help
+```