Chore: Add Facebook app set up documentation (#647)

Co-authored-by: Pranav Raj S <pranavrajs@gmail.com>

docs/channels/facebook-channel.md

@@ -0,0 +1,40 @@
+---
+path: "/docs/channels/facebook"
+title: "How to create Facebook channel?"
+---
+
+If you are using self-hosted Chatwoot installation, please configure the Facebook app as described in the [guide to setup Facebook app](/docs/facebook-setup)
+
+**Step 1**. Click on "Add Inbox" button from Settings > Inboxes page.
+
+![fb_create](./images/facebook/inbox_create.png)
+
+**Step 2**. Click on "Facebook" icon.
+
+![list_of_channels](./images/facebook/list_of_channels.png)
+
+**Step 3**. Click on Facebook login button. It will open a new window for you to login.
+
+![create_fb](./images/facebook/login_with_facebook.png)
+
+**Step 4**. Authenticate with Facebook and select the page you want connect, enable all permissions shown in the list, otherwise the app might not work.
+
+![link_account](./images/facebook/link_account.png)
+
+![list_of_pages](./images/facebook/list_of_pages.png)
+
+![list_of_pages](./images/facebook/permissions.png)
+
+![select_page](./images/facebook/select_page.png)
+
+**Step 5**. "Add agents" to your Facebook inbox.
+
+![add_agents](./images/add_agents.png)
+
+**Step 6**. Hooray! You have sucessfully created a Facebook inbox. Whenever a customer sends a message to your Facebook page, you will be able to see it here and manage it.
+
+![finish_inbox](./images/facebook/finish_inbox.png)
+
+**Step 7**. If you want to update the agents who have access to the inbox, you can go to Settings > Inboxes.
+
+![inbox_settings](./images/inbox_settings.png)