Add the ability to swap the to/from currencies

[CliffAw]

Description

Add the ability to swap the currencies between to/from, so that a user can quickly swap between the two values.

Note: This is an extension of the functionality implemented in #1.

Acceptance Criteria

Given... The application is running
And... The currencies request is functioning
And... There has been no conversion yet made
When... I select a button to swap the to/from values
Then... The currency and rate values in the in the inputs are swapped

Given... The application is running
And... The currencies request is functioning
And... There has been a conversion made and the conversion result is outputted into the UI
When... I select a button to swap the to/from values
Then... The currency and rate values in the in the inputs are swapped
And... The conversion result panel should be highlighted indicating the result is no longer valid and "Convert" button should be pressed again

Assets

Before conversion result:

After conversion result, before swapping currencies

After conversion result, after swapping currencies