PowerShell: Add MIME type to SharePoint

Add-SPAllowedInlineDownloadedMimeType.ps1

function Add-SPAllowedInlineDownloadedMimeType{
    [CmdLetBinding()]
    param(
        [Parameter(Mandatory=$true, Position=0, ValueFromPipeLine=$true)]
        [Microsoft.SharePoint.PowerShell.SPWebApplicationPipeBind]$WebApplication,
        [Parameter(Mandatory=$true, Position=1)]
        [string]$MimeType
    )
    process{
        $actualWebApp = $WebApplication.Read()
        if ($actualWebApp.AllowedInlineDownloadedMimeTypes -notcontains $mimetype)
        {
           Write-Host "Adding MIME Type..."
           $actualWebApp.AllowedInlineDownloadedMimeTypes.Add($mimetype)
           $actualWebApp.Update()
           Write-Host "Done."
        } Else {
           Write-Host -ForegroundColor Green "MIME type is already added."
        }
    }
}

use.ps1

Add-SPAllowedInlineDownloadedMimeType -WebApplication http://mywebapp -MimeType "text/html"