Improve hint text display on hover

[PhilReedData]

Describe the bug

• There is hint text for the properties of events and materials which shows on mouse-over of the text fields.
• This text is reportedly missed by users, feedback from Flemish RDM group.
  • There is no visual prompt that hint text exists, such as ⓘ.
  • The hint takes too long to appear after user moves cursor over text field.
  • There is no way to show this instructional content without a mouse.
• Propose to include a visual indication of the hint, a text-based indication for screen readers, and increase the speed that the hint appears in. Or, show the hints at all times, like we do with the 'Sponsors' field (perhaps with 'show more' for long hints).

To Reproduce

Steps to reproduce the behavior:

1. Edit or create new event or material.
2. Hover over text fields.

Expected behavior

Hint should show faster and be clearer, with a more accessible option for visually impaired users.

Additional context

Follows on from ElixirTeSS/docs#8 and #1174