add message commands docs

Author: notunderctrl

apps/website/docs/guide/02-commands/01-chat-input-commands.mdx

@@ -2,9 +2,12 @@
 title: Chat input commands
 ---
 
+Chat input commands, more commonly known as 'Slash Commands', are a
+way for users on Discord to perform actions using your bot.
+
 CommandKit provides a very simple way to manage your chat input
-(slash) commands, including registering them to the Discord API, as
-well as handling their execution.
+commands, including registering them to the Discord API, as well as
+handling their execution.
 
 To create a new chat input command, create a new file in the
 `src/app/commands` directory with the name of the command. This guide

apps/website/docs/guide/02-commands/02-command-options-autocomplete.mdx

@@ -4,7 +4,8 @@ title: Options autocomplete
 
 :::warning
 
-This feature is only available for chat input (slash) commands.
+This feature is only available for
+[chat input commands](./01-chat-input-commands.mdx).
 
 :::
 

apps/website/docs/guide/02-commands/04-message-commands.mdx

@@ -1,3 +1,67 @@
 ---
 title: Message commands
 ---
+
+Message commands, which are generally considered 'Legacy', are a way
+to run commands on Discord bots using regular messages. Before the
+introduction of
+[Slash/Chat Input Commands](./01-chat-input-commands.mdx), this was
+the primary way commands were handled. They were usually triggered by
+using a prefix set by the developer of the bot (for example: `!ping`).
+
+:::warning
+
+While CommandKit allows developers to create and handle message
+commands, it's important to note that Discord generally discourages
+message commands in favor of the more modern
+[Chat Input Commands](./01-chat-input-commands.mdx).
+
+:::
+
+Message commands, like all the other command types, live in your
+`src/app/commands` directory. To let CommandKit know that this is a
+message command, just export the `messageCommand` function.
+
+```ts title="src/app/commands/ping.ts"
+import type { CommandData, MessageCommand } from 'commandkit';
+
+export const command: CommandData = {
+  name: 'ping',
+};
+
+export const messageCommand: MessageCommand = async (ctx) => {
+  await ctx.message.reply('Pong!');
+};
+```
+
+:::tip
+
+By default, your bot's prefix will be `!`. However, with CommandKit
+you can set custom prefixes, or even guild-based prefixes.
+[Read more](./05-custom-message-commands-prefix.mdx)
+
+:::
+
+## Message command options (arguments)
+
+Since a message command - on a technical level - is just a string, the
+idea of message command options will be different compared to
+[chat input command](./01-chat-input-commands.mdx) options. Instead of
+getting parsed data, you'll essentially be dealing with string
+'arguments'.
+
+```ts title="src/app/commands/ping.ts"
+import type { CommandData, MessageCommand } from 'commandkit';
+
+export const command: CommandData = {
+  name: 'ping',
+};
+
+export const messageCommand: MessageCommand = async (ctx) => {
+  const args = ctx.message.args(); // string[]
+};
+```
+
+With the above command as an example, if a user on Discord runs
+`!ping arg1 arg2 arg3`, the value of `args` will equal
+`['arg1', 'arg2', 'arg3']`.