docs: Update Installation.md (#6650)

Added links for Fluidd/Mainsail/Octoprint

Added references to overview.md and mkdocs.yml and spelling errors.

Signed-off-by: James Hartley <james@hartleyns.com>

docs/OctoPrint.md

@@ -0,0 +1,79 @@
+# OctoPrint for Klipper
+
+Klipper has a few options for its front ends, Octoprint was the first
+and original front end for Klipper. This document will give
+a brief overview of installing with this option.
+
+## Install with OctoPi
+
+Start by installing [OctoPi](https://github.com/guysoft/OctoPi) on the
+Raspberry Pi computer. Use OctoPi v0.17.0 or later - see the
+[OctoPi releases](https://github.com/guysoft/OctoPi/releases) for
+release information.
+
+One should verify that OctoPi boots and that the
+OctoPrint web server works. After connecting to the OctoPrint web
+page, follow the prompt to upgrade OctoPrint if needed.
+
+After installing OctoPi and upgrading OctoPrint, it will be necessary
+to ssh into the target machine to run a handful of system commands.
+
+Start by running these commands on your host device:
+
+__If you do not have git installed, please do so with:__
+```
+sudo apt install git
+```
+then proceed:
+```
+cd ~
+git clone https://github.com/Klipper3d/klipper
+./klipper/scripts/install-octopi.sh
+```
+
+The above will download Klipper, install the needed system dependencies,
+setup Klipper to run at system startup, and start the Klipper host
+software. It will require an internet connection and it may take a few
+minutes to complete.
+
+## Installing with KIAUH
+
+KIAUH can be used to install OctoPrint on a variety of Linux based systems
+that run a form of Debian. More information can be found
+at https://github.com/dw-0/kiauh
+
+## Configuring OctoPrint to use Klipper
+
+The OctoPrint web server needs to be configured to communicate with the Klipper
+host software. Using a web browser, login to the OctoPrint web page and then
+configure the following items:
+
+Navigate to the Settings tab (the wrench icon at the top of the page).
+Under "Serial Connection" in "Additional serial ports" add:
+
+```
+~/printer_data/comms/klippy.sock
+```
+Then click "Save".
+
+_In some older setups this address may be `/tmp/printer`_
+
+
+Enter the Settings tab again and under "Serial Connection" change the "Serial Port"
+setting to the one added above.
+
+In the Settings tab, navigate to the "Behavior" sub-tab and select the
+"Cancel any ongoing prints but stay connected to the printer" option. Click "Save".
+
+From the main page, under the "Connection" section (at the top left of the page)
+make sure the "Serial Port" is set to the new additional one added
+and click "Connect". (If it is not in the available selection then
+try reloading the page.)
+
+Once connected, navigate to the "Terminal" tab and type "status" (without the quotes)
+into the command entry box and click "Send". The terminal window will likely report
+there is an error opening the config file - that means OctoPrint is successfully
+communicating with Klipper.
+
+Please proceed to [Installation.md](Installation.md) and the
+_Building and flashing the micro-controller_ section