(#3) Adds Discord Notification Plugin

Adds a Discord notification plugin, similar to the Gitter implementation.

Has two options for posting, a simple text output identical to the default Gitter notification and a more complex Discord-specific card.

src/Plugins/Discord.ps1

@@ -0,0 +1,76 @@
+<#
+.SYNOPSIS
+  Publishes the package update status to Discord.
+
+.LINK
+  https://discord.com/developers/docs/resources/webhook#execute-webhook
+#>
+[CmdletBinding(DefaultParameterSetName="Url")]
+param(
+  [Parameter(Mandatory)]
+  $Info,
+
+  # This is the Discord Webhook ID
+  [Parameter(Mandatory, ParameterSetName="Id")]
+  [string]$WebhookId,
+
+  # This is the Discord webhook token.
+  [Parameter(Mandatory, ParameterSetName="Id")]
+  [string]$WebhookToken,
+
+  # This is the full custom webhook url created in Discord.
+  [Parameter(Mandatory, ParameterSetName="Url")]
+  [string]$WebHookUrl = "https://discord.com/api/webhooks/$($WebhookId)/$($WebhookToken)",
+
+  # If set, just sends a simple text message.
+  [switch]$Simple
+)
+
+if ($WebHookUrl -eq "https://discord.com/api/webhooks//") { return } # If we don't have a valid webhookurl we can't push status messages, so ignore.
+
+$updatedPackages   = @($Info.result.updated).Count
+$publishedPackages = @($Info.result.pushed).Count
+$failedPackages    = $Info.error_count.total
+$gistUrl           = $Info.plugin_results.Gist -split '\n' | Select-Object -Last 1
+$packageCount      = $Info.result.all.Length
+
+$Body = if ($Simple) {
+  @{
+    content = 
+      "[Update Status: $($packageCount) packages.`n" +
+      "$($updatedPackages) updated, $($publishedPackages) Published, $($failedPackages) Failed]($($gistUrl))"
+  }
+} else {
+  @{
+    embeds = @(
+      @{
+        title = "Packages Updated"
+        description = "$($packageCount) packages were updated$(if ($failedPackages -gt 0) {", with **$($failedPackages) failure**"})."
+        timestamp = Get-Date $Info.startTime -Format "yyyy-MM-ddThh:mm:ss.000zzz"
+        url = $gistUrl
+        color = if ($failedPackages -gt 0) {"15548997"} else {"0"}
+        fields = @(
+          @{name = "Total"; value = "$($packageCount)"; inline = $false}
+          @{name = "Updated"; value = "$($updatedPackages)"; inline = $true}
+          @{name = "Published"; value = "$($publishedPackages)"; inline = $true}
+          @{name = "Failed"; value = "$($failedPackages)"; inline = $true}
+        )
+        footer = @{
+          text = "Run took $($Info.minutes) minutes."
+        }
+      }
+    )
+  }
+}
+
+$arguments = @{
+  Body             = $Body | ConvertTo-Json -Depth 5
+  UseBasicParsing  = $true
+  Uri              = $WebHookUrl
+  ContentType      = 'application/json'
+  Method           = 'POST'
+}
+
+Write-Host "Submitting message to Discord"
+Invoke-RestMethod @arguments
+Write-Host "Message submitted to Discord"

src/Plugins/Gitter.ps1

@@ -5,7 +5,7 @@
   Publishes the package update status to gitter.
 
 .PARAMETER WebHookUrl
-  This is the cusotm webhook url created through gitter integrations.
+  This is the custom webhook url created through gitter integrations.
 
 .PARAMETER MessageFormat
   The format of the message that is meant to be published on gitter.