chore: Import PSDocs module in PSDocs.Common.Tests.ps1

Import the PSDocs module in the PSDocs.Common.Tests.ps1 file to ensure that the necessary dependencies are available for testing.

tests/PSDocs.Tests/PSDocs.Common.Tests.ps1

@@ -43,6 +43,7 @@ Describe 'PSDocs instance names' -Tag 'Common', 'InstanceName' {
                 InputObject = $dummyObject
                 OutputPath  = $outputPath
             }
+            Import-Module (Join-Path -Path $rootPath.Path -ChildPath out/modules/PSDocs) -Force;
         }
         $result = Invoke-PSDocument @invokeParams -Name 'WithoutInstanceName';
         It 'Should generate an output named WithoutInstanceName.md' {