extension semantic loader examples
    .js returns module exports path-replace-loader
    .ts returns module exports ts-loader
    .coffee returns module exports coffee-loader
    coffee-redux-loader
    .jsx returns module exports (react component) jsx-loader
    react-hot-loader!jsx-loader
    .json
    .json5    		 returns json value json-loader
    json5-loader
    .txt return string value raw-loader
    .css returns nothing, side effect of adding style to DOM style-loader!css-loader
    style-loader!css-loader!autoprefixer-loader
    .less returns nothing, side effect of adding style to DOM style-loader!css-loader!less-loader
    .scss returns nothing, side effect of adding style to DOM style-loader!css-loader!scss-loader
    .styl returns nothing, side effect of adding style to DOM style-loader!css-loader!stylus-loader
    .png
    .jpg
    .jpeg
    .gif
    .svg    		 returns url to image file-loader
    url-loader
    .woff
    .ttf    		 returns url to font file-loader
    url-loader
    .wav
    .mp3    		 returns url to audio file-loader
    url-loader
    .mpeg
    .mp4
    .webm
    .ogv    		 returns url to video file-loader
    .html returns HTML as string html-loader
    .md
    .markdown    		 returns HTML as string html-loader!markdown-loader
    .jade returns template function jade-loader
    .hbs
    .handlebars    		 returns template function handlebars-loader