Merge the main branch from https://github.com/aarnott/Library.Template

Specifically, this merges [4d2be89 from that repo](AArnott/Library.Template@4d2be89).

Author: AArnott

tools/Install-NuGetPackage.ps1

@@ -0,0 +1,55 @@
+<#
+.SYNOPSIS
+    Installs a NuGet package.
+.PARAMETER PackageID
+    The Package ID to install.
+.PARAMETER Version
+    The version of the package to install. If unspecified, the latest stable release is installed.
+.PARAMETER Source
+    The package source feed to find the package to install from.
+.PARAMETER PackagesDir
+    The directory to install the package to. By default, it uses the Packages folder at the root of the repo.
+.PARAMETER ConfigFile
+    The nuget.config file to use. By default, it uses :/nuget.config.
+.OUTPUTS
+    System.String. The path to the installed package.
+#>
+[CmdletBinding(SupportsShouldProcess=$true,ConfirmImpact='Low')]
+Param(
+    [Parameter(Position=1,Mandatory=$true)]
+    [string]$PackageId,
+    [Parameter()]
+    [string]$Version,
+    [Parameter()]
+    [string]$Source,
+    [Parameter()]
+    [switch]$Prerelease,
+    [Parameter()]
+    [string]$PackagesDir="$PSScriptRoot\..\packages",
+    [Parameter()]
+    [string]$ConfigFile="$PSScriptRoot\..\nuget.config",
+    [Parameter()]
+    [ValidateSet('Quiet','Normal','Detailed')]
+    [string]$Verbosity='normal'
+)
+
+$nugetPath = & "$PSScriptRoot\Get-NuGetTool.ps1"
+
+try {
+    Write-Verbose "Installing $PackageId..."
+    $nugetArgs = "Install",$PackageId,"-OutputDirectory",$PackagesDir,'-ConfigFile',$ConfigFile
+    if ($Version) { $nugetArgs += "-Version",$Version }
+    if ($Source) { $nugetArgs += "-FallbackSource",$Source }
+    if ($Prerelease) { $nugetArgs += "-Prerelease" }
+    $nugetArgs += '-Verbosity',$Verbosity
+
+    if ($PSCmdlet.ShouldProcess($PackageId, 'nuget install')) {
+        $p = Start-Process $nugetPath $nugetArgs -NoNewWindow -Wait -PassThru
+        if ($null -ne $p.ExitCode -and $p.ExitCode -ne 0) { throw }
+    }
+
+    # Provide the path to the installed package directory to our caller.
+    Write-Output (Get-ChildItem "$PackagesDir\$PackageId.*")[0].FullName
+} finally {
+    Pop-Location
+}