A11Y: Icons in your table should be using proper alt text

On the page [Working With Git - Best Practices](https://esdc-devcop.github.io/guides/source-control/working-with-git.html)

You should be using descriptive alternative text for your icons in the table.

```
<img class="emoji" title=":heavy_check_mark:" alt=":heavy_check_mark:" src="https://github.githubassets.com/images/icons/emoji/unicode/2714.png" width="20" height="20">
```