Improvement: Implement shinyGovstyle inputs across the app

[JT-39]

Improvement Overview

Would be nice to have consistently styled inputs across the app by utilising the functions from the {shinyGovstyle}package.

Current Issue

They main location where this is an issue is the Create Your Own page where there is a mixture of {shiny}, {shinyGovstyle} and {shinyWidgets} inputs. This means they need slightly different styling adjustments and don't quite all look from the same family.

Proposed Enhancement

By using the {shinyGovstyle} package and its inbuilt input options, there should be a way round this inconsistent styling problem.

Impact

Makes the app look more professional, the current formatting is slightly jarring to look at.

Additional Information

Only thing is that the input to select the Year Range may not have a direct replacement in the {shinyGovstyle} package, so either a workaround is needed with an existing input or need to lockdown the styling of a different package to align with the others. (This is sort of currently what is being done but the Year Range input is slightly off.)