Adding script for generating types

... and not ignoring non-public .d.ts files... because it's fine if they're packaged

Author: weaverryan

dist/util/get-stimulus-comment-options.d.ts

@@ -0,0 +1,4 @@
+export default function (source: string): {
+    options: {};
+    errors: any[];
+};

dist/webpack/create-controllers-module.d.ts

@@ -0,0 +1,4 @@
+export default function createControllersModule(config: any): {
+    finalSource: string;
+    deprecations: string[];
+};

dist/webpack/generate-lazy-controller.d.ts

@@ -0,0 +1 @@
+export default function (controllerPath: string, indentationSpaces: number, exportName?: string): string;

package.json

@@ -11,6 +11,7 @@
     },
     "scripts": {
         "build": "yarn rollup -c",
+        "build-types": "yarn tsc",
         "test": "yarn run webpack --config test/webpack.config.js && yarn run jest",
         "lint": "yarn run eslint src test",
         "format": "prettier src/*.ts test/*.js --write",