Document Silent Messages.

Hey folks!

This is actually my 2022 hackweek project which I got to finish to
completion. :)

During a message send request, if you include the new
`SUPPRESS_NOTIFICATIONS` flag it will not broadcast any push/desktop
notifications but will still increment the relevant mention counters.

The intention is that you can get someone's attention but not feel like
you could be distracting them. Like when you DM someone at 5am. I'm sure some
bots can leverage this as well to avoid noise or something.

Also this should work for the webhook send request as well.

[Add a picture of the UI here]

If you're looking to leverage this as a non-bot, you can write `@silent`
as the _very first_ thing in a message. Make sure your client is
up-to-date btw. Autocomplete a-la `@everyone` is not planned. Eventually we may
put this in an "actual UI", for now this is where it lives. :)

Also sorry to all the users on Discord named silent who may have some
textual conflict now. Forgive me!

Author: tpcstld

docs/resources/Channel.md

@@ -359,17 +359,18 @@ Represents a message sent in a channel within Discord.
 
 ###### Message Flags
 
-| Flag                                   | Value  | Description                                                                       |
-| -------------------------------------- | ------ | --------------------------------------------------------------------------------- |
-| CROSSPOSTED                            | 1 << 0 | this message has been published to subscribed channels (via Channel Following)    |
-| IS_CROSSPOST                           | 1 << 1 | this message originated from a message in another channel (via Channel Following) |
-| SUPPRESS_EMBEDS                        | 1 << 2 | do not include any embeds when serializing this message                           |
-| SOURCE_MESSAGE_DELETED                 | 1 << 3 | the source message for this crosspost has been deleted (via Channel Following)    |
-| URGENT                                 | 1 << 4 | this message came from the urgent message system                                  |
-| HAS_THREAD                             | 1 << 5 | this message has an associated thread, with the same id as the message            |
-| EPHEMERAL                              | 1 << 6 | this message is only visible to the user who invoked the Interaction              |
-| LOADING                                | 1 << 7 | this message is an Interaction Response and the bot is "thinking"                 |
-| FAILED_TO_MENTION_SOME_ROLES_IN_THREAD | 1 << 8 | this message failed to mention some roles and add their members to the thread     |
+| Flag                                   | Value   | Description                                                                       |
+| -------------------------------------- | ------  | --------------------------------------------------------------------------------- |
+| CROSSPOSTED                            | 1 << 0  | this message has been published to subscribed channels (via Channel Following)    |
+| IS_CROSSPOST                           | 1 << 1  | this message originated from a message in another channel (via Channel Following) |
+| SUPPRESS_EMBEDS                        | 1 << 2  | do not include any embeds when serializing this message                           |
+| SOURCE_MESSAGE_DELETED                 | 1 << 3  | the source message for this crosspost has been deleted (via Channel Following)    |
+| URGENT                                 | 1 << 4  | this message came from the urgent message system                                  |
+| HAS_THREAD                             | 1 << 5  | this message has an associated thread, with the same id as the message            |
+| EPHEMERAL                              | 1 << 6  | this message is only visible to the user who invoked the Interaction              |
+| LOADING                                | 1 << 7  | this message is an Interaction Response and the bot is "thinking"                 |
+| FAILED_TO_MENTION_SOME_ROLES_IN_THREAD | 1 << 8  | this message failed to mention some roles and add their members to the thread     |
+| SUPPRESS_NOTIFICATIONS                 | 1 << 12 | this message will not trigger push and desktop notifications                      |
 
 ###### Example Message