Added helper script.

update-submodules.ps1

@@ -0,0 +1,37 @@
+#!/bin/pwsh
+
+param (
+    [Parameter(Mandatory = $true)]
+    [string]
+    $Version
+)
+
+$root = $PSScriptRoot
+$jellyfinApiModulePath = "$root/src/jellyfin/jellyfin" | Resolve-Path
+$jellyfinWebModulePath = "$root/src/jellyfin-web/jellyfin-web" | Resolve-Path
+
+Write-Host "Updating sub-modules to '$Version'."
+
+try
+{
+    Push-Location $jellyfinApiModulePath
+    git fetch --all
+    git checkout $Version
+}
+finally
+{
+    Pop-Location
+}
+
+try
+{
+    Push-Location $jellyfinWebModulePath
+    git fetch --all
+    git checkout $Version
+}
+finally
+{
+    Pop-Location
+}
+
+Write-Host "Done!"