update dev env and delete stale yarnpkg repo (#33)

.devcontainer/pre-setup.sh

@@ -1,6 +1,11 @@
 #!/bin/bash
 set -e
 
+# workaround for devimage
+sudo find /etc/apt/sources.list.d -maxdepth 1 -type f -exec \
+	sh -c 'grep -q "dl.yarnpkg.com/debian" "$1" && rm -f "$1" || true' _ {} \;
+sudo sed -i '/dl.yarnpkg.com\/debian/d' /etc/apt/sources.list || true
+
 sudo apt update -y
 sudo apt install -y curl
 sudo apt-get install -y docker.io