feat(explorer): implement map fn argument

Add a function for mapping over all FileNodes as an option for `Explorer`

quartz/components/ExplorerNode.tsx

@@ -9,6 +9,7 @@ export interface Options {
   useSavedState: boolean
   sortFn: (a: FileNode, b: FileNode) => number
   filterFn?: (node: FileNode) => boolean
+  mapFn?: (node: FileNode) => void
 }
 
 type DataWrapper = {
@@ -86,6 +87,16 @@ export class FileNode {
     this.children = filteredNodes
   }
 
+  /**
+   * Filter FileNode tree. Behaves similar to `Array.prototype.map()`, but modifies tree in place
+   * @param mapFn function to filter tree with
+   */
+  map(mapFn: (node: FileNode) => void) {
+    mapFn(this)
+
+    this.children.forEach((child) => child.map(mapFn))
+  }
+
   /**
    * Get folder representation with state of tree.
    * Intended to only be called on root node before changes to the tree are made