Add ability to evaluate `tailwind.config.js` file if exists

[praveenperera]

Get custom sorter by evaluating tailwind.config.js file

Features

• Pass with --tailwind-sorter can accept value (value would be path to tailwind-config.js
• If value not passed in look for tailwind.config.js somewhere within the home directory
• Use postcss to evaluate file, get classes from file and use that order

Implementation

• Build up HashMap of classes from running regex on evaluated file
• Save HashMap to disk using serde and bincode
• Check tailwind.config.js metadata to see if new HashMap should get created