Create Home Office button component

[tomyems]

Using the NotGovUK button component (with GOV.UK styling) and signposting to the GOV.UK design system guidance on the use of buttons, create a Home Office button component, with the only difference being styling of the secondary button equivalent to that described in the discussion: #372 (comment).

[tomyems]

There's an attempt on branch https://github.com/UKHomeOffice/design-system/tree/515-new-button-component to:

• create a HomeOfficeButton component that extends the NotGovUK component replacing 'govuk-button' with 'hods-button'
• update the status message component to use styling like the secondary button component

This branch has a number of issues:

• no tests
• does all the GOV.UK design system button functionality work, such as disabled, warning and so on (and what's the best way to future proof against further improvements)?
• the status message uses links styled as buttons, is this best, or should it use the button component

Also, do we need a new component name, like HomeOfficeButton, as this conflicts with the naming convention for the other components?

There are more GOV.UK components that we might 'just' need to apply Home Office styling to, such as tabs and tags, so we need a consistent way of developing these.

[tomyems]

P.S. the branch is deployed: https://645e60090a414800b0b99c78--hods.netlify.app/components?name=Button