add privileged flag to devcontainer, to flash from vscode

.devcontainer/devcontainer.json

@@ -0,0 +1,13 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/docker-existing-dockerfile
+{
+	"name": "sonar_fpga",
+	"build": {
+		// Sets the run context to one level up instead of the .devcontainer folder.
+		"context": "..",
+		// Update the 'dockerFile' property if you aren't using the standard 'Dockerfile' filename.
+		"dockerfile": "../Dockerfile"
+	},
+
+	"runArgs": ["--privileged"]
+}

BUILDING.md

@@ -7,9 +7,6 @@ The recommended dev flow if you want to make changes is to use VSCode with remot
 it's the easiest way to get the toolchain up and running, and to fix the issues encountered
 with migen.
 
-*Note: I currently do not know how to run the dev container with --privileged, so you'll need
-to flash by manually running it*
-
 Recommended extensions:
 
 - Pylance