Include tooltips for MAAP registration form

[smohiudd]

Description

From slack message (Rishi Verma):

Page 3 (Registration Form):
It would be helpful to have some tool tips or descriptions for some of the fields just to give more context. For example:
Institution: "Your organization or university"
Project: "Science mission or research project name"
Sponsor Name: "PI or supervisor approving your access"
Funding Source: "Grant, agency, or program funding your work"
Actually, I'm also wondering what the difference between "Sponsor Name" and "Funding Source" is - can we combine them?
Username field: add help text "This will be your JupyterHub workspace name"

Acceptance Criteria

• MAAP User registration includes tooltips

[smohiudd]

cc: @wildintellect