Firmware now builds in a VSCode "Remote Container"

.devcontainer/Dockerfile

@@ -0,0 +1,15 @@
+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/blob/v0.241.1/containers/debian/.devcontainer/base.Dockerfile
+
+# [Choice] Debian version (use bullseye on local arm64/Apple Silicon): bullseye, buster
+ARG VARIANT=bullseye
+FROM mcr.microsoft.com/vscode/devcontainers/base:${VARIANT}
+
+RUN    apt update \
+    && apt upgrade -y \
+    && apt install -y \
+        build-essential git wget binfmt-support qemu gcc-9 \
+        parted gcc-avr avr-libc avrdude python3 python3-tornado curl \
+        unzip python3-setuptools gcc-arm-linux-gnueabihf bc sudo \
+    && update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 9 \
+    && curl -fsSL https://deb.nodesource.com/setup_18.x | bash - \
+    && apt install -y nodejs