wix: include zstd.pyd in the installation

When trying to create a zstd bundle, the MSI based install said:

  abort: compression engine zstd could not be loaded

The Inno installer is unaffected.  The name will need to be updated to include
'cext' when merging into default.

contrib/wix/dist.wxs

@@ -1,35 +1,36 b''
 <?xml version="1.0" encoding="utf-8"?>
 <Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
 
   <?include guids.wxi ?>
   <?include defines.wxi ?>
 
   <Fragment>
     <DirectoryRef Id="INSTALLDIR" FileSource="$(var.SourceDir)">
       <Component Id="distOutput" Guid="$(var.dist.guid)" Win64='$(var.IsX64)'>
         <File Name="python27.dll" KeyPath="yes" />
       </Component>
       <Directory Id="libdir" Name="lib" FileSource="$(var.SourceDir)/lib">
         <Component Id="libOutput" Guid="$(var.lib.guid)" Win64='$(var.IsX64)'>
           <File Name="library.zip" KeyPath="yes" />
           <File Name="mercurial.base85.pyd" />
           <File Name="mercurial.bdiff.pyd" />
           <File Name="mercurial.diffhelpers.pyd" />
           <File Name="mercurial.mpatch.pyd" />
           <File Name="mercurial.osutil.pyd" />
           <File Name="mercurial.parsers.pyd" />
+          <File Name="mercurial.zstd.pyd" />
           <File Name="pyexpat.pyd" />
           <File Name="bz2.pyd" />
           <File Name="select.pyd" />
           <File Name="unicodedata.pyd" />
           <File Name="_ctypes.pyd" />
           <File Name="_elementtree.pyd" />
           <File Name="_hashlib.pyd" />
           <File Name="_socket.pyd" />
           <File Name="_ssl.pyd" />
         </Component>
       </Directory>
     </DirectoryRef>
   </Fragment>
 
 </Wix>