add color to text github readme code example

Example 1: how to add color in text github readme

```diff
- text in red
+ text in green
! text in orange
# text in gray
@@ text in purple (and bold)@@
```

Example 2: readme.md text color

```json
   // code for coloring
```
```html
   // code for coloring
```
```js
   // code for coloring
```
```css
   // code for coloring
```
// etc.