Add a run shell script which wraps invoke with the correct venv

Author: jacob-hughes

run

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+PYTHON=${PYTHON:-python3}
+VENV_DIR=".venv"
+
+if [ ! -d "$VENV_DIR" ]; then
+    $PYTHON -m venv "$VENV_DIR"
+    . "$VENV_DIR/bin/activate"
+    pip install --upgrade pip
+    pip install .[dev]
+fi
+
+. "$VENV_DIR/bin/activate"
+
+invoke "$@"