State allowed resume file extension on registration page

[cameronbrill]

Is your feature request related to a problem? Please describe.
When a user registers, the system assumes the user knows that pdf is the only allowed file extension when submitting a resume. When one tries submitting an application with a resume that is not a pdf, the user gets an error, stating that the only allowed file extension is pdf.

Describe the solution you'd like
Instead of telling them after the fact, state the allowed file extension in the registration page, perhaps next to the "Companies will use this resume to offer interviews for internships and full-time positions." text block.

Additional context