Example how to add formated key and value to json file with powershell.

AddJsonKey.ps1

param([Parameter(Mandatory)]$key, [Parameter(Mandatory)]$value, $file='.\i18n.json')

if ($value -eq $null) {
  $value = read-host -Prompt "Please enter a value" 
}

function Format-Json([Parameter(Mandatory, ValueFromPipeline)][String] $json) {
    $indent = 0;
    ($json -Split "`n" | % {
        if ($_ -match '[\}\]]\s*,?\s*$') {
            # This line ends with ] or }, decrement the indentation level
            $indent--
        }
        $line = ('  ' * $indent) + $($_.TrimStart() -replace '":  (["{[])', '": $1' -replace ':  ', ': ')
        if ($_ -match '[\{\[]\s*$') {
            # This line ends with [ or {, increment the indentation level
            $indent++
        }
        $line
    }) -Join "`n"
}

$json = Get-Content $file | Out-String | ConvertFrom-Json
$json | Add-Member -Type NoteProperty -Name $key -Value $value -Force
$json | Select-Object ($json | Get-Member -MemberType NoteProperty).Name | ConvertTo-Json | Format-Json | Set-Content $file