Varadrane7 added back to top

[varadrane7]

(todo:please remove this todo and the sections you did not check below before you make your pull request. If you are unsure, please check other PRs like this one: https://github.com/hackerkid/Mind-Expanding-Books/pull/207#issue-377268434)

In this pull request

• [ ] I am adding a new book.
• [ ] I am adding a new category
• [ ] Removing a book
• [x] Added Back to Top button after every section

380

[hackerkid]

This looks great. Merged. Thanks!