Upgrade chokidar and fsevents for Apple M1 compatibility (#3945)

This PR updates `chokidar` and `fsevents` in package.json.

`fsevents` ~2.1.2 was deprecated, and mentions to use 2.2 or 2.3 instead. This is the message you see when installing rollup as a dependency: `rollup > fsevents@2.1.3: "Please update to latest v2.3 or v2.2"`. The [commits](https://github.com/fsevents/fsevents/commits/master) there imply it's for Apple M1 compatibility.

`chokidar` also updated to that version of `fsevents`, so I updated that here too.

If you see package-lock.json, you'll see the older version of 2.1.3 got added to mocha's dependencies. They use the older version, and haven't released a new version yet.

package.json

@@ -55,7 +55,7 @@
   },
   "homepage": "https://rollupjs.org/",
   "optionalDependencies": {
-    "fsevents": "~2.1.2"
+    "fsevents": "~2.3.1"
   },
   "devDependencies": {
     "@rollup/plugin-alias": "^3.1.1",
@@ -75,7 +75,7 @@
     "acorn-static-class-features": "^0.2.4",
     "acorn-walk": "^8.0.1",
     "buble": "^0.20.0",
-    "chokidar": "^3.4.3",
+    "chokidar": "^3.5.1",
     "codecov": "^3.8.1",
     "colorette": "^1.2.1",
     "core-js": "^3.8.2",