Add env var for cache file

import json

import os

import os.path

import threading

import time

from modules.paths import data_path, script_path

cache_filename = os.path.join(data_path, "cache.json")

cache_filename = os.environ.get('SD_WEBUI_CACHE_FILE', os.path.join(data_path, "cache.json"))

cache_data = None

cache_lock = threading.Lock()