lint(types): typecheck d.ts in cosmic-swingset

Author: turadg

packages/cosmic-swingset/tsconfig.json

@@ -1,6 +1,9 @@
 // This file can contain .js-specific Typescript compiler config.
 {
   "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "skipLibCheck": false
+  },
   "include": [
     "calc-*.js",
     "src/**/*.js",