doc: README.rst added to subsys/console/echo sample

README added to the console echo sample

Signed-off-by: ingram weeks <ingram.weeks@gmail.com>

samples/subsys/console/echo/README.rst

@@ -0,0 +1,43 @@
+.. zephyr:code-sample:: console_echo
+   :name: Console echo
+   :relevant-api: console_api
+
+   Echo an input character back to the output using the Console API.
+
+Overview
+********
+
+This example shows how the :c:func:`console_getchar` and
+:c:func:`console_putchar` functions can be used to echo an input character
+back to the console.
+
+Requirements
+************
+
+UART console is required to run this sample.
+
+Building and Running
+********************
+
+Build and flash the sample as follows, changing ``nucleo_f401re`` for your
+board. Alternatively you can run this using QEMU, as described in
+:zephyr:code-sample:`console_getchar`.
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/console/echo
+   :host-os: unix
+   :board: nucleo_f401re
+   :goals: build flash
+   :compact:
+
+Following the initial prompt given by the firmware, start pressing keys on a
+keyboard, and they will be echoed back to the terminal program you are using.
+
+Sample Output
+=============
+
+.. code-block:: console
+
+    You should see another line with instructions below. If not,
+    the (interrupt-driven) console device doesn't work as expected:
+    Start typing characters to see them echoed back