Devcontainer (#7697)

Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

.devcontainer/devcontainer.json

@@ -0,0 +1,31 @@
+{
+  "name": "Home Assistant Frontend",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "context": ".."
+  },
+  "appPort": 8123,
+  "context": "..",
+  "postCreateCommand": "script/bootstrap",
+  "extensions": [
+    "github.vscode-pull-request-github",
+    "dbaeumer.vscode-eslint",
+    "ms-vscode.vscode-typescript-tslint-plugin",
+    "esbenp.prettier-vscode",
+    "bierner.lit-html",
+    "runem.lit-plugin",
+    "ms-python.vscode-pylance"
+  ],
+  "settings": {
+    "terminal.integrated.shell.linux": "/bin/bash",
+    "files.eol": "\n",
+    "editor.tabSize": 2,
+    "editor.formatOnPaste": false,
+    "editor.formatOnSave": true,
+    "editor.formatOnType": true,
+    "[typescript]": {
+      "editor.defaultFormatter": "esbenp.prettier-vscode"
+    },
+    "files.trimTrailingWhitespace": true
+  }
+}