Add devcontainer

Signed-off-by: Christian König <ckoenig@posteo.de>

.devcontainer/devcontainer.json

@@ -0,0 +1,23 @@
+{
+  "name": "Pi-hole web devcontainer",
+  "dockerFile": "Dockerfile",
+	// Use 'postCreateCommand' to run commands after the container is created.
+	"postCreateCommand": "npm install",
+	"customizations": {
+		// Configure properties specific to VS Code.
+		"vscode": {
+			"settings": {},
+			"extensions": [
+				"eamodio.gitlens",
+				"EditorConfig.EditorConfig",
+                "github.vscode-github-actions"
+			]
+		}
+	},
+  "containerEnv": {
+    "GIT_EDITOR": "nano"
+  },
+  "mounts": [
+    "type=bind,source=/home/${localEnv:USER}/.ssh,target=/root/.ssh,readonly"
+  ]
+}