Re-add mypy script

tools/mypy.sh

+#!/usr/bin/env bash
+set -e -u
+
+if [ ! -f sdkconfig.defaults ] || [ ! -f recovery/sdkconfig.defaults ]; then
+    echo >/dev/stderr "Run this script for the root of the repository (ie. tools/mypy.sh)."
+    exit 1
+fi
+
+export MYPYPATH=$(pwd)/python_payload/mypystubs:$(pwd)/python_payload
+echo "Checking st3m..."
+
+_CI="${CI:-}"
+
+if [ ! -z "${_CI}" ]; then
+    : > warnings.txt
+fi
+
+failed=""
+function _mypy() {
+    if [ ! -z "${_CI}" ]; then
+        mypy "$1" --strict --no-color-output >> warnings.txt || failed=true
+    else
+        mypy "$1" --strict || failed=true
+    fi
+}
+
+_mypy python_payload/main.py
+for f in python_payload/apps/*/flow3r.toml; do
+    app_name="$(basename $(dirname $f))"
+    echo "Checking ${app_name}..."
+    _mypy python_payload/apps/${app_name}
+done
+
+if [ $failed ]; then
+    echo "Failed"
+    exit 1
+fi