Add language slugs (various areas)

[gewarren]

Prep for dotnet/docs#45892.

(Hide whitespace changes.)

[learn-build-service-prod]

Learn Build status updates of commit a4f936d:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/Microsoft.VisualBasic.Compatibility.VB6/DirListBox.xml	✅Succeeded	View
xml/Microsoft.VisualBasic.Compatibility.VB6/FileListBox.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/BulletChrome.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/ButtonChrome.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/ClassicBorderDecorator.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/DataGridHeaderBorder.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/ListBoxChrome.xml	✅Succeeded	View
xml/Microsoft.Windows.Themes/ScrollChrome.xml	✅Succeeded	View
xml/System.Activities.Presentation/ActivityDesigner.xml	✅Succeeded	View
xml/System.ComponentModel.Design/DesignerTransaction.xml	✅Succeeded	View
xml/System.ComponentModel/ICustomTypeDescriptor.xml	✅Succeeded	View
xml/System.IdentityModel.Services.Configuration/FederationConfiguration.xml	✅Succeeded	View
xml/System.IdentityModel.Services/WSFederationAuthenticationModule.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementCreateAttribute.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementEntityAttribute.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementNameAttribute.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementQualifierAttribute.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementQualifierFlavors.xml	✅Succeeded	View
xml/System.Management.Instrumentation/ManagementReferenceAttribute.xml	✅Succeeded	View
xml/System.Management.Instrumentation/WmiConfigurationAttribute.xml	✅Succeeded	View
xml/System.ServiceModel.Channels/ReliableSessionBindingElement.xml	✅Succeeded	View
xml/System.ServiceModel.Security.Tokens/SecureConversationSecurityTokenParameters.xml	✅Succeeded	View
xml/System.ServiceModel/ServiceBehaviorAttribute.xml	✅Succeeded	View

For more details, please refer to the build report.

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[BillWagner]

This LGTM. Let's