Add markdown preview, update rust.vim

sources_non_forked/markdown-preview.nvim/app/install.cmd

@@ -0,0 +1,29 @@
+@PowerShell -ExecutionPolicy Bypass -Command Invoke-Expression $('$args=@(^&{$args} %*);'+[String]::Join(';',(Get-Content '%~f0') -notmatch '^^@PowerShell.*EOF$')) & goto :EOF
+
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+$repo = "iamcco/markdown-preview.nvim"
+$file = "markdown-preview-win.zip"
+
+$releases = "https://api.github.com/repos/$repo/releases"
+
+Write-Host Determining latest release
+if ($args[0]) { $tag = $args[0] } else { $tag = (Invoke-WebRequest $releases | ConvertFrom-Json)[0].tag_name }
+
+$download = "https://github.com/$repo/releases/download/$tag/$file"
+$name = $file.Split(".")[0]
+$zip = "$name-$tag.zip"
+$dir = "bin"
+
+new-item -Name $dir -ItemType directory -Force
+
+Write-Host Dowloading latest release
+Invoke-WebRequest $download -Out $zip
+
+Remove-Item $dir\* -Recurse -Force -ErrorAction SilentlyContinue
+
+Write-Host Extracting release files
+Expand-Archive $zip -DestinationPath $dir -Force
+
+Remove-Item $zip -Force
+Write-Host markdown-preview install completed.