New `MessageType` documented

[vicky5124]

https://github.com/discord/discord-api-docs/commit/e5cd463cd1412df2e55fce8ecb81e7d1ed5755b0 documented new Message Types:

| GUILD_APPLICATION_PREMIUM_SUBSCRIPTION       | 32    | true      |
| GUILD_INCIDENT_ALERT_MODE_ENABLED            | 36    | true      |
| GUILD_INCIDENT_ALERT_MODE_DISABLED           | 37    | true      |
| GUILD_INCIDENT_REPORT_RAID                   | 38    | true      |
| GUILD_INCIDENT_REPORT_FALSE_ALARM            | 39    | true      |

And messages of the type GUILD_APPLICATION_PREMIUM_SUBSCRIPTION can now be deleted.

This affects src/model/channel/message.rs#972