Added documentation for PM2 (#2105)

* Added PM2 documentation

* Grammar fix

* Build error fix.

* Just work T_T

* Update docs/autostart_pm2.rst

Co-Authored-By: Vexed <51716387+Vexed01@users.noreply.github.com>

* Update docs/autostart_pm2.rst

Co-Authored-By: Vexed <51716387+Vexed01@users.noreply.github.com>

* Create 2105.docs.rst

changelog.d/2105.docs.rst

@@ -0,0 +1 @@
+Added documentation for PM2 support.

docs/autostart_pm2.rst

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+.. pm2 service guide
+
+==============================================
+Setting up auto-restart using pm2 on Linux
+==============================================
+
+.. note:: This guide is for setting up PM2 on a Linux environment. This guide assumes that you already have a working Red instance.
+
+--------------
+Installing PM2
+--------------
+
+Start by installing Node.JS and NPM via your favorite package distributor. From there run the following command:
+
+:code:`npm install pm2 -g`
+
+After PM2 is installed, run the following command to enable your Red instance to be managed by PM2. Replace the brackets with the required information.
+You can add additional Red based arguments after the instance, such as :code:`--dev`.
+
+:code:`pm2 start redbot --name "<Insert a name here>" --interpreter "<Location to your Python Interpreter>" -- <Red Instance> --no-prompt`
+
+.. code-block:: none
+
+    Arguments to replace.
+
+    --name ""
+    A name to identify the bot within pm2, this is not your Red instance.
+
+    --interpreter ""
+    The location of your Python interpreter, to find out where that is use the following command:
+    which python3.6
+
+    <Red Instance>
+    The name of your Red instance.
+
+------------------------------
+Ensuring that PM2 stays online
+------------------------------
+
+To make sure that PM2 stays online and persistence between machine restarts, run the following commands:
+
+:code:`pm2 save` & :code:`pm2 startup`

docs/index.rst

@@ -16,6 +16,7 @@ Welcome to Red - Discord Bot's documentation!
     install_linux_mac
     venv_guide
     autostart_systemd
+    autostart_pm2
 
 .. toctree::
     :maxdepth: 2