cache: Hide IsResourceDir from the exported config

cache/filecache/filecache_config.go

@@ -93,7 +93,7 @@ type FileCacheConfig struct {
 
 	// Will resources/_gen will get its own composite filesystem that
 	// also checks any theme.
-	IsResourceDir bool
+	IsResourceDir bool `json:"-"`
 }
 
 // GetJSONCache gets the file cache for getJSON.

docs/data/docs.yaml

@@ -910,27 +910,21 @@ config:
   caches:
     assets:
       dir: :resourceDir/_gen
-      isResourceDir: true
       maxAge: -1
     getcsv:
       dir: :cacheDir/:project
-      isResourceDir: false
       maxAge: -1
     getjson:
       dir: :cacheDir/:project
-      isResourceDir: false
       maxAge: -1
     getresource:
       dir: :cacheDir/:project
-      isResourceDir: false
       maxAge: -1
     images:
       dir: :cacheDir/images
-      isResourceDir: false
       maxAge: 1.8e+15
     modules:
       dir: :cacheDir/modules
-      isResourceDir: false
       maxAge: -1
   canonifyURLs: false
   cascade: []