Better a11y around mask inputs for a11y

[cy-by]

What

Interesting choice that the input for a SSN is using type="tel". This poses a11y issues.

I first though it should move to type="number" but gov.uk recently moved their number inputs to:

<input type="text" inputmode="numeric" pattern="[0-9]*">

Investigate if this pattern is worth adopting.

Why

Discovered when investigating #265.