Update several package versions

These changes were generated by comparing with the latest cookiecutter

Author: mwcraig

package.json

@@ -5,9 +5,14 @@
   "keywords": [
     "jupyter",
     "jupyterlab",
-    "jupyterlab extension",
+    "jupyterlab-extension",
     "widgets"
   ],
+  "files": [
+    "lib/**/*.js",
+    "dist/*.js",
+    "css/*.css"
+  ],
   "homepage": "https://github.com/jupyter-widgets/jupyterlab-sidecar",
   "bugs": {
     "url": "https://github.com/jupyter-widgets/jupyterlab-sidecar/issues"
@@ -42,17 +47,26 @@
     "watch:labextension": "jupyter labextension watch ."
   },
   "dependencies": {
-    "@jupyter-widgets/base": "6.0.0-rc.0",
-    "@jupyter-widgets/jupyterlab-manager": "5.0.0-rc.0",
+    "@jupyter-widgets/base": "^4 || ^5 || ^6",
+    "@jupyter-widgets/jupyterlab-manager": "^3 || ^4 || ^5",
     "@jupyterlab/application": "^3.0.0",
     "@lumino/coreutils": "^1.5.3"
   },
   "devDependencies": {
+    "@babel/core": "^7.5.0",
+    "@babel/preset-env": "^7.5.0",
     "@jupyterlab/builder": "^3.0.0",
     "@types/expect.js": "^0.3.29",
     "@types/mocha": "^7.0.2",
     "@types/node": "^13.9.2",
+    "@types/webpack-env": "^1.13.6",
+    "@typescript-eslint/eslint-plugin": "^3.6.0",
+    "@typescript-eslint/parser": "^3.6.0",
     "expect.js": "^0.3.1",
+    "css-loader": "^3.2.0",
+    "eslint": "^7.4.0",
+    "eslint-config-prettier": "^6.11.0",
+    "eslint-plugin-prettier": "^3.1.4",
     "fs-extra": "^8.1.0",
     "json-loader": "^0.5.7",
     "karma": "^4.4.1",
@@ -65,10 +79,12 @@
     "mkdirp": "^1.0.3",
     "mocha": "^7.1.1",
     "npm-run-all": "^4.1.5",
+    "prettier": "^2.0.5",
     "rimraf": "^3.0.2",
-    "source-map-loader": "^0.2.4",
-    "ts-loader": "^6.2.1",
-    "typescript": "^3.8.3"
+    "source-map-loader": "^1.1.3",
+    "style-loader": "^1.0.0",
+    "ts-loader": "^8.0.0",
+    "typescript": "~4.1.3"
   },
   "jupyterlab": {
     "extension": "lib/plugin",
@@ -83,9 +99,5 @@
         "singleton": true
       }
     }
-  },
-  "resolutions": {
-    "@jupyter-widgets/base": "6.0.0-rc.0",
-    "@jupyter-widgets/jupyterlab-manager": "5.0.0-rc.0"
   }
 }