update installation instructions and add mpv handler setup script

scripts/install-mpv-handler.ps1

@@ -129,6 +129,29 @@ function Get-MpvPathFromConfig {
   }
 }
 
+function Resolve-CommandPath {
+  param(
+    [Parameter(Mandatory = $true)]
+    [string[]]$Names
+  )
+
+  foreach ($name in $Names) {
+    try {
+      $command = Get-Command -Name $name -ErrorAction Stop
+      if ($command.Path) {
+        return $command.Path
+      }
+
+      if ($command.Source) {
+        return $command.Source
+      }
+    } catch {
+    }
+  }
+
+  return $null
+}
+
 function Remove-ProtocolKey {
   param(
     [Parameter(Mandatory = $true)]
@@ -204,7 +227,12 @@ $effectiveIconPath = if ($IconPath) {
   }
   (Resolve-Path -LiteralPath $IconPath).Path
 } else {
-  Get-MpvPathFromConfig -ConfigPath $configPath
+  $configuredPath = Get-MpvPathFromConfig -ConfigPath $configPath
+  if ($configuredPath) {
+    $configuredPath
+  } else {
+    Resolve-CommandPath -Names @('mpv.com', 'mpv.exe', 'mpv')
+  }
 }
 
 if (-not $effectiveIconPath) {