Adding axis labels for a line chart

* [x] I've read, understood, and done my best to follow the [*CONTRIBUTING guidelines](https://github.com/jjatie/Charts/blob/master/CONTRIBUTING.md).

## What did you do?

ℹ I read a lot of other peoples problems and went through the android repository ℹ and could not find the answer to my problem.

## What did you expect to happen?

ℹ I need labels on the x and y axis. On the y axis I need it to say Depth(m) and the ℹ x axis needs to say Time(days)

## What happened instead?

ℹ Nothing happened.

## Charts Environment

**Charts version/Branch/Commit Number:**
**Xcode version:**
**Swift version:**
**Platform(s) running Charts:**
**macOS version running Xcode:**

## Demo Project

ℹ Please link to or upload a project we can download that reproduces the issue.