add "prettier" formatter

ui/.devcontainer/devcontainer.json

@@ -22,6 +22,7 @@
 			// Add the IDs of extensions you want installed when the container is created.
 			"extensions": [
 				"dbaeumer.vscode-eslint",
+				"esbenp.prettier-vscode",
 				"mhutchie.git-graph",
 				"Syler.sass-indented",
 				"Vue.volar"

ui/.vscode/settings.json

@@ -1,5 +1,14 @@
 {
   "editor.formatOnSave": true,
+  "[vue]": {
+    "editor.defaultFormatter": "esbenp.prettier-vscode"
+  },
+  "[typescript]": {
+    "editor.defaultFormatter": "esbenp.prettier-vscode"
+  },
+  "[javascript]": {
+    "editor.defaultFormatter": "esbenp.prettier-vscode"
+  },
   "editor.codeActionsOnSave": {
     "source.organizeImports": true
   },
@@ -7,5 +16,6 @@
   "editor.tabSize": 2,
   "sass.disableAutoIndent": true,
   "sass.format.convert": false,
-  "sass.format.deleteWhitespace": true
+  "sass.format.deleteWhitespace": true,
+  "prettier.trailingComma": "all",
 }