Add language slugs (System.Web)

[gewarren]

Prep for dotnet/docs#45892.

(Hide whitespace changes.)

[learn-build-service-prod]

Learn Build status updates of commit e4656bc:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Web.Caching/SqlCacheDependency.xml	✅Succeeded	View
xml/System.Web.Compilation/RouteUrlExpressionBuilder.xml	✅Succeeded	View
xml/System.Web.Compilation/RouteValueExpressionBuilder.xml	✅Succeeded	View
xml/System.Web.Configuration/AuthorizationSection.xml	✅Succeeded	View
xml/System.Web.Configuration/ClientTarget.xml	✅Succeeded	View
xml/System.Web.Configuration/ClientTargetCollection.xml	✅Succeeded	View
xml/System.Web.Configuration/ClientTargetSection.xml	✅Succeeded	View
xml/System.Web.Configuration/HttpCapabilitiesBase.xml	✅Succeeded	View
xml/System.Web.Configuration/HttpHandlerAction.xml	✅Succeeded	View
xml/System.Web.Configuration/HttpHandlersSection.xml	✅Succeeded	View
xml/System.Web.Configuration/HttpModulesSection.xml	✅Succeeded	View
xml/System.Web.Configuration/PagesEnableSessionState.xml	✅Succeeded	View
xml/System.Web.Configuration/PagesSection.xml	✅Succeeded	View
xml/System.Web.Configuration/PassportAuthentication.xml	✅Succeeded	View
xml/System.Web.Configuration/SessionStateSection.xml	✅Succeeded	View
xml/System.Web.DynamicData/DynamicControl.xml	✅Succeeded	View
xml/System.Web.DynamicData/DynamicField.xml	✅Succeeded	View
xml/System.Web.Management/WebFailureAuditEvent.xml	✅Succeeded	View
xml/System.Web.Profile/ProfileGroupBase.xml	✅Succeeded	View
xml/System.Web.Profile/ProfileManager.xml	✅Succeeded	View
xml/System.Web.Routing/PageRouteHandler.xml	✅Succeeded	View
xml/System.Web.Routing/UrlRoutingHandler.xml	✅Succeeded	View
xml/System.Web.Script.Serialization/JavaScriptTypeResolver.xml	✅Succeeded	View
xml/System.Web.Security.AntiXss/AntiXssEncoder.xml	✅Succeeded	View
xml/System.Web.Security/ActiveDirectoryMembershipProvider.xml	✅Succeeded	View

This comment lists only the first 25 files in the pull request.
For more details, please refer to the build report.

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[gewarren]

Ping @Rick-Anderson