Added and fixed a bunch of docs stuff (#1767)

- Fixed a common copy paste fail `the the <thing>` in various places
- Apparently I can't type Resolvable correctly,
Fixed that wherever applicable
- Documented GroupDMChannel#nicks so that it will be displayed on the docs
- GroupDMChannel#icon is nullable
- Removed empty InviteOptions typdef, as its properties are now documented in GuildChannel#createInvite
- MessageMentions#channels is no longer nullable
- RoleData#permissions takes a PermissionResolvable or an array of them
- Webhook#avatar is nullable
- Added HTTPOptions typedef and added it to ClientOptions typedef
- ClientUserChannelOverride#muted is for a channel and not a guild directly

src/structures/Role.js

@@ -186,7 +186,7 @@ class Role {
    * @property {ColorResolvable} [color] The color of the role, either a hex string or a base 10 number
    * @property {boolean} [hoist] Whether or not the role should be hoisted
    * @property {number} [position] The position of the role
-   * @property {string[]} [permissions] The permissions of the role
+   * @property {PermissionResolvable|PermissionResolvable[]} [permissions] The permissions of the role
    * @property {boolean} [mentionable] Whether or not the role should be mentionable
    */