Customize Hexa color skins

Hexa 5 is using tailwind CSS to manage and generate skins.

1. Download dev zip. Download `hexa5-dev.zip` and extract `hexa5-dev` folder on local computer. 
2. Copy template files. Copy `templates` folder from latest hexa5.zip\upload into `hexa5-dev`. PurgeCSS will scan the `templates` folder to remove all unused CSS.
3. Install NPM packages. Open command line and run `npm install`
4. Build CSS Skins. Example build commands for "tailwind-core.css", "tailwind-original.css" and "tailwind-city.css".
   "npm run build:core"
   "npm run build:original"
   "npm run build:city"
   Minified skin files will be placed into hexa/assets/css/skins/ and hexa-light/assets/css/skins/ folders.
5. Custom Skin. Create "tailwind-cucstom.css" (initial values can be copied from existing skins and customized) and run "npm run build:custom". Custom skin can be selected from Hexa Extras general tab.