Integrate "/convert" API into conversion UI

[SilverBirchh]

Description

Add the ability to complete the conversion of one currency to another for a specific amount.

The API already exists for this and can be accessed at: /convert

Acceptance Criteria

Given... The application is running
And... The convert API request is functioning
When... I add in a valid currency code as the "From" value
And... I add in a valid currency code as the "To" value
And... I add in a valid amount
Then... The currency conversion button should become enabled
And... When clicked, the /convert API should be called with the entered values
And... The result outputted into the UI

Stretch Goal

Add handling of non-valid currency codes to the UI to make clear that the currency code submitted is not supported.

Assets

Before conversion:

After conversion: