Add command to test/check code in dev-setup docs

dev-setup.md

@@ -2,6 +2,8 @@
 
 ## Lint / format extensions
 
+Setting these in the IDE give a better developer experience auto-formatting code on save and providing instant feedback on lint issues.
+
 ### VSCode
 Install Prettier, ESLint and Svelte extensions.
 
@@ -23,3 +25,8 @@ in User `settings.json` (`cmd + shift + p` and search for Open User Settings JSO
   "eslint.validate": ["javascript", "svelte"]
 }
 ```
+
+## Running tests / checks
+
+In both server and web:
+`npm run check:all`