The SSRS team announced that a PowerShell module is available that supports SQL Server Reporting Services (SSRS) in PowerShell.
To get this new module just run this command in your PowerShell console:
Invoke-Expression (Invoke-WebRequest https://aka.ms/rstools)
After the module has finished downloading and you have it unpacked you can run this command to list available SSRS commands:
Get-Command -Module ReportingServicesTools