Add node_modules until bundler is added

node_modules/fast-diff/diff.d.ts

@@ -0,0 +1,20 @@
+declare function diff(
+    text1: string,
+    text2: string,
+    cursorPos?: number | diff.CursorInfo
+): diff.Diff[];
+
+declare namespace diff {
+    type Diff = [-1 | 0 | 1, string];
+
+    const DELETE: -1;
+    const INSERT: 1;
+    const EQUAL: 0;
+
+    interface CursorInfo {
+        oldRange: { index: number; length: number };
+        newRange: { index: number; length: number };
+    }
+}
+
+export = diff;