feat: add support for VSCode Dev Containers

This cannot be used in codespaces due to the extra mount, but it does allow for local development.

.devcontainer/bin/copy-plugin

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+main() {
+  declare PLUGIN_NAME="$1"
+
+  make go-build-plugin copyplugin PLUGIN_NAME=$PLUGIN_NAME
+}
+
+main "$@"