build: switch from .npmignore to files field in package.json (#92)

Author: dsanders11

.npmignore

@@ -16,6 +16,10 @@
     "electron-docs-linter": "./dist/bin.js",
     "electron-docs-parser": "./dist/bin.js"
   },
+  "files": [
+    "dist",
+    "!dist/__tests__"
+  ],
   "devDependencies": {
     "@continuous-auth/semantic-release-npm": "^3.0.0",
     "@types/chai": "^4.2.5",