feat(explorer): integrate filter option

quartz/components/Explorer.tsx

@@ -35,6 +35,11 @@ export default ((userOpts?: Partial<Options>) => {
     // Sort tree (folders first, then files (alphabetic))
     fileTree.sort(opts.sortFn!)
 
+    // If provided, apply filter function to fileTree
+    if (opts.filterFn) {
+      fileTree.filter(opts.filterFn)
+    }
+
     // Get all folders of tree. Initialize with collapsed state
     const folders = fileTree.getFolderPaths(opts.folderDefaultState === "collapsed")
 

quartz/components/ExplorerNode.tsx

@@ -8,6 +8,7 @@ export interface Options {
   folderClickBehavior: "collapse" | "link"
   useSavedState: boolean
   sortFn: (a: FileNode, b: FileNode) => number
+  filterFn?: (node: FileNode) => boolean
 }
 
 type DataWrapper = {
@@ -66,6 +67,10 @@ export class FileNode {
     this.children.forEach((e) => e.print(depth + 1))
   }
 
+  /**
+   * Filter FileNode tree. Behaves similar to `Array.prototype.filter()`, but modifies tree in place
+   * @param filterFn function to filter tree with
+   */
   filter(filterFn: (node: FileNode) => boolean) {
     const filteredNodes: FileNode[] = []