Chat docs (#108)

* Initial Chat draft

* Chat docs

* Chat CSP

* Fix lint

_snippets/chat/customization.mdx

@@ -0,0 +1,22 @@
+```typescript
+Plain.init({
+  appId: '<YOUR_CHAT_APP_ID>',
+
+  // Hides the launcher, you can manually show it by calling `Plain.open()` (default: false)
+  hideLauncher: false,
+
+  // The title of the chat window shown on the Welcome screen
+  title: 'Chat with us',
+
+  // A collection of links shown on the Welcome screen
+  links: [
+    {
+      text: 'View our docs',
+      url: 'https://www.plain.com/docs',
+    },
+  ],
+
+  // The color of your brand which will be used in parts of the Chat as well as the launcher color
+  brandColor: '#000000',
+});
+```

chat.mdx

@@ -0,0 +1,44 @@
+---
+title: 'Chat'
+sidebarTitle: 'Overview'
+---
+
+_Chat is currently in Beta. This will not effect the reliability of this feature but we are heavily iterating and improving on the featureset._
+
+Our Chat widget lets you embed a live chat interface on your website or app, allowing your customers to reach out to you without leaving your site. You can then respond to these messages directly from Plain.
+
+You and the customer can communicate in real-time and provide high fidelity support including syntax highlighting and rich-text formatting.
+
+Here’s how to get started:
+
+<Steps>
+  <Step title="Create your Chat app">
+    *At the moment you can only create a single Chat app configuration per workspace. In future we
+    will allow multiple configurations.* - In Plain, navigate to **`Settings`** > **`Chat`**. -
+    Press **`Create Chat App`**.
+  </Step>
+  <Step title="Add Chat to your webpage(s)">
+    After creating your Chat app, you will be provided with a snippet of code that you can embed in
+    your website or app. This will add the chat widget to your site. We recommend adding this to all
+    pages of your site.
+  </Step>
+  <Step title="Customize your Chat experience">
+    You can customize some aspects of the Chat widget by providing additional information to the
+    `Plain.init` function. These are the available options:
+    <Snippet file="chat/customization.mdx" />
+  </Step>
+  <Step title="Viewing Chats in Plain">
+    Each new conversation in the Chat widget creates a new thread in Plain. You can view and respond
+    to these threads in the Plain app.
+  </Step>
+</Steps>
+
+## Content Security Policy (CSP)
+
+If you are using a Content Security Policy on your website, you will need to add the following to your CSP:
+
+```text
+script-src https://cdn.plain.com;
+connect-src https://chat.uk.plain.com;
+style-src https://fonts.googleapis.com;
+```

mint.json

@@ -91,6 +91,12 @@
 						"slack/data-retention"
 					]
 				},
+				{
+					"group": "Chat",
+					"pages": [
+						"chat"
+					]
+				},
 				{
 					"group": "Microsoft Teams",
 					"pages": [