chore: add note about hidden input

src/features/FileUploader/FileUploader.styled.ts

@@ -2,6 +2,18 @@ import { Typography } from '@equinor/eds-core-react'
 import styled from 'styled-components'
 import { spacings } from '../../tokens/spacings'
 
+/*
+  Note: Hiding the input element because it is ugly,
+  difficult to style and inconsistent in design
+  across browsers. It can be activated by clicking the label,
+  so we style the label like a styled link Typography, so
+  the user will know to interact with it to upload files.
+
+  opacity is used to hide the input, because assistive
+  tech interprets visibility: hidden or display: none
+  to mean that the file input isn't interactive
+*/
+
 const FileUpload = styled.label`
   display: flex;
   align-items: center;