chore(rollup): add auto externals plugin

I'm keeping the existing external key because the auto externals plugin
doesn't capture @babel/runtime.

Author: floryst

package-lock.json

@@ -104,6 +104,7 @@
     "prettier": "2.4.0",
     "process": "0.11.10",
     "rollup": "2.56.3",
+    "rollup-plugin-auto-external": "2.0.0",
     "rollup-plugin-copy": "3.4.0",
     "rollup-plugin-ignore": "1.0.10",
     "rollup-plugin-polyfill-node": "0.7.0",

package.json

@@ -16,6 +16,7 @@ import { string } from 'rollup-plugin-string';
 import svgo from 'rollup-plugin-svgo';
 import webworkerLoader from 'rollup-plugin-web-worker-loader';
 import copy from 'rollup-plugin-copy';
+import autoExternal from 'rollup-plugin-auto-external';
 
 import packageJSON from './package.json';
 
@@ -98,6 +99,7 @@ export default {
   },
   external: Object.keys(packageJSON.dependencies).map((name) => new RegExp(`^${name}`)),
   plugins: [
+    autoExternal(),
     alias({
       entries: [
         { find: 'vtk.js', replacement: path.resolve(__dirname) },