Implement diff highlight (#85)

* diff highlight

* update docs and function renaming

* fix

* simplify code

* lint code

* lint code

* rename classes

* solution through split func

* update code style

* remove line numbers testing

* Update main.css

public/dist/code-styling.css

@@ -1 +1,2 @@
 .hljs{display:block;background:#fff;padding:.5em;color:#333;overflow-x:auto}.hljs-comment,.hljs-meta{color:#969896}.hljs-emphasis,.hljs-quote,.hljs-string,.hljs-strong,.hljs-template-variable,.hljs-variable{color:#df5000}.hljs-keyword,.hljs-selector-tag,.hljs-type{color:#a71d5d}.hljs-attribute,.hljs-bullet,.hljs-literal,.hljs-symbol{color:#0086b3}.hljs-name,.hljs-section{color:#63a35c}.hljs-tag{color:#333}.hljs-attr,.hljs-selector-attr,.hljs-selector-class,.hljs-selector-id,.hljs-selector-pseudo,.hljs-title{color:#795da3}.hljs-addition{color:#55a532;background-color:#eaffea}.hljs-deletion{color:#bd2c00;background-color:#ffecec}.hljs-link{text-decoration:underline}
+.diff{display:inline-block;width:100%}.diff span{color:inherit!important}.diff--added{color:#277030;background-color:#e2fce7}.diff--added:before{content:"+";opacity:.4}.diff--removed{color:#ae363c;background-color:#ffe6e6}.diff--removed:before{content:"-";opacity:.4}