add task to update snapshots & update readme (#1302)

* add task to update snapshots & update readme

* remove test:app from readme & tweak

README.md

@@ -39,15 +39,14 @@ git clone https://github.com/excalidraw/excalidraw.git
 
 #### Commands
 
-| Command             | Description                       |
-| ------------------- | --------------------------------- |
-| `npm install`       | Install the dependencies          |
-| `npm start`         | Run the project                   |
-| `npm run fix`       | Reformat all files with Prettier  |
-| `npm run test:code` | Test for formatting with Prettier |
-| `npm run test:app`  | Test the app                      |
-| `npm run test`      | Run all tests                     |
-| `npm run test -u`   | Update all snapshots              |
+| Command               | Description                       |
+| --------------------- | --------------------------------- |
+| `npm install`         | Install the dependencies          |
+| `npm start`           | Run the project                   |
+| `npm run fix`         | Reformat all files with Prettier  |
+| `npm test`            | Run tests                         |
+| `npm run test:update` | Update test snapshots             |
+| `npm run test:code`   | Test for formatting with Prettier |
 
 ## Contributing
 

package.json

@@ -109,6 +109,7 @@
     "prettier": "prettier \"**/*.{css,scss,json,md,html,yml}\" --ignore-path=.eslintignore",
     "start": "react-scripts start",
     "test": "npm run test:app",
+    "test:update": "npm run test:app -- --updateSnapshot --watchAll=false",
     "test:app": "react-scripts test --env=jsdom --passWithNoTests",
     "test:code": "eslint --max-warnings=0 --ignore-path .gitignore --ext .js,.ts,.tsx .",
     "test:debug": "react-scripts --inspect-brk test --runInBand --no-cache",