Add namespace case for NavigatorIndex.PageType.

Author: mportiz08

Sources/SwiftDocC/Indexing/Navigator/NavigatorIndex.swift

@@ -309,6 +309,9 @@ public class NavigatorIndex {
         case languageGroup = 127
         case container = 254
         case groupMarker = 255 // UInt8.max
+
+        // C++ symbols
+        case namespace = 48
 
         /// Initialize a page type from a `role` and a `symbolKind` returning the Symbol type.
         init(symbolKind: String) {
@@ -336,6 +339,7 @@ public class NavigatorIndex {
             case "enumcm", "structcm", "clm", "intfcm", "type.method": self = .typeMethod
             case "httpget", "httpput", "httppost", "httppatch", "httpdelete": self = .httpRequest
             case "dict": self = .dictionarySymbol
+            case "namespace": self = .namespace
             default: self = .symbol
             }
         }

Sources/SwiftDocC/Indexing/RenderIndexJSON/RenderIndex.swift

@@ -364,6 +364,8 @@ extension NavigatorIndex.PageType {
             return "httpRequest"
         case .dictionarySymbol:
             return "dictionarySymbol"
+        case .namespace:
+            return SymbolGraph.Symbol.KindIdentifier.namespace.renderingIdentifier
         case .propertyListKeyReference:
             return "propertyListKeyReference"
         case .languageGroup: