Fix/remove examples and docs from package (#2557)

* Fix #2337: remove `examples` and `docs` from npm package

* Add `directories` property but only with the directories that are still in the npm package

Author: josdejong

package.json

@@ -127,9 +127,7 @@
   "files": [
     "bin",
     "dist",
-    "docs",
     "lib",
-    "examples",
     "main",
     "types",
     "number.cjs",
@@ -139,6 +137,10 @@
     "HISTORY.md",
     "CONTRIBUTING.md"
   ],
+  "directories": {
+    "bin": "./bin",
+    "lib": "./lib"
+  },
   "scripts": {
     "build": "gulp --gulpfile gulpfile.cjs && npm run update-authors",
     "build-and-test": "npm run build && npm run test:all && npm run lint",
@@ -171,13 +173,6 @@
   "bugs": {
     "url": "https://github.com/josdejong/mathjs/issues"
   },
-  "directories": {
-    "doc": "./docs",
-    "example": "./examples",
-    "lib": "./lib",
-    "src": "./src",
-    "test": "./test"
-  },
   "browserslist": [
     "IE 11"
   ],