wip: replace packages with pure files

packages/file-graph/errors.ts

@@ -0,0 +1,21 @@
+/* eslint-disable max-classes-per-file */
+export class DuplicateItemError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = 'DuplicateItemError'
+  }
+}
+
+export class ParentNotExistsError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = 'ParentNotExistsError'
+  }
+}
+
+export class FileNotExistsError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = 'FileNotExistsError'
+  }
+}