fix(build): copy the flow type info into dist.

index.js.flow

@@ -0,0 +1,10 @@
+type SourceLocation = {
+  line: number;
+  column: number;
+};
+
+declare class LinesAndColumns {
+  constructor(string: string): void;
+  locationForIndex(index: number): ?SourceLocation;
+  indexForLocation(location: SourceLocation): ?number;
+}

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "flow": "flow check --all",
     "prebuild": "rm -rf dist",
-    "build": "rollup -c",
+    "build": "rollup -c && cp index.js.flow dist/lines-and-columns.js.flow",
     "pretest": "npm run build",
     "test": "mocha",
     "prepublish": "npm run flow && npm run build",