Simplified zip creation and added an all-in-one zip, closes #35.

[CptMoore]

This now allows the following:

  <Target Name="DoorstopFetch" BeforeTargets="CopyFilesToGame" Condition="'$(BattleTechGameDir)' != '' And !Exists('$(BattleTechGameDir)\winhttp.dll')">
    <PropertyGroup>
      <DoorstopUrl>https://github.com/CptMoore/UnityDoorstop/releases/download/ci/doorstop_all_in_one_4.0.0.zip</DoorstopUrl>
    </PropertyGroup>
    <DownloadFile SourceUrl="$(DoorstopUrl)" DestinationFolder="$(DoorstopIntDir)" />
    <Unzip SourceFiles="$(DoorstopIntDir)\doorstop_all_in_one_4.0.0.zip" DestinationFolder="$(DoorstopIntDir)" />
    <Copy SourceFiles="$(DoorstopIntDir)\doorstop_win_release\x64\winhttp.dll" DestinationFolder="$(BattleTechGameDir)" />
    <Copy SourceFiles="$(DoorstopIntDir)\doorstop_linux_release\x64\libdoorstop.so" DestinationFolder="$(BattleTechGameDir)" />
    <Copy SourceFiles="$(DoorstopIntDir)\doorstop_macos_release\x64\libdoorstop.dylib" DestinationFolder="$(BattleTechGameDir)" />
  </Target>

[ghorsington]

Overall looks nice! Here's one comment though on the name.