Support Multiple Steps

Support for renaming downloaded item

now you can use the column B to rename the file before saving to your file system

• rename feature added
• ~10 ✖️faster processing items with batch downloads 🚀
• Content security Policy added to renderer
• upgrade to electron 7 🎉
• event based communication is handled through preload script
• disable node Integration
• enable context isolation
• upgrage to babel 7
• upgrade to core-js 3