Prepends markdown files with frontmatter for docusaurus

add-frontmatter.ps1

Get-ChildItem  -recurse -Filter *.md | `
Foreach-Object{    
    $content = Get-Content $_.FullName

    $frontmatter = New-Object -TypeName "System.Text.StringBuilder"
    
    [void]$frontmatter.AppendLine("---");
    [void]$frontmatter.AppendLine( "id: $($_.basename.ToLower()) ");
    [void]$frontmatter.AppendLine("---");

    Set-Content $_.FullName -value $frontmatter.ToString(), $content    
}