docs: prepare documentation for readthedocs

This commit adds mkdocs.yml and modifies the existing markdown documentation so that  "readthedocs" can build documentation using "mkdocs".

Included are many formatting changes and fixes to the existing documentation so that it shows up correctly when published.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

docs/user_changes.md

@@ -1,3 +1,4 @@
+##
 This file will track changes that require user intervention,
 such as a configuration change or a reinstallation.
 
@@ -33,10 +34,10 @@ such as a configuration change or a reinstallation.
   This changes requires the user to rerun the install script.  If
   `moonraker.conf` is not located in the home directory, the command
   will looks something like the following:
-  ```
-  cd ~/moonraker
-  ./scripts/install-moonraker.sh -f -c /home/pi/klipper_config/moonraker.conf
-  ```
+
+        cd ~/moonraker
+        ./scripts/install-moonraker.sh -f -c /home/pi/klipper_config/moonraker.conf
+
   Otherwise you can run the install script with no arguments.
 
 ### November 19th 2020
@@ -49,24 +50,24 @@ such as a configuration change or a reinstallation.
   will update the defaults file wih the new path.
 - New dependencies have been added to Moonraker which require reinstallation.
   Run the following command to reinstall and rebuild the virtualenv:
-  ```
-  ~/moonraker/scripts/install-moonraker.sh -r
-  ```
+
+        ~/moonraker/scripts/install-moonraker.sh -r
+
 - The power plugin configuration has changed.  See the
   [install guide](installation.md#power-control-plugin) for
   details on the new configuration.
 - Users transitioning from the previous version of the power plugin will need
   to unexport any curently used pins.  For example, the following command
   may be used to unexport pin 19:
-  ```
-  echo 19 > /sys/class/gpio/unexport
-  ```
+
+        echo 19 > /sys/class/gpio/unexport
+
   Alternatively one may reboot the machine after upgrading:
-  ```
-  cd ~/moonraker/
-  git pull
-  ~/moonraker/scripts/install-moonraker.sh -r
-  sudo reboot
-  ```
+
+    cd ~/moonraker/
+    git pull
+    ~/moonraker/scripts/install-moonraker.sh -r
+    sudo reboot
+
   Make sure that the power plugin configuration has been updated prior
   to rebooting the machine.