Standardize "opt-in" language for Comms and UX surveys

We should write and approve some standard language to use in surveys that will allow users to opt-in to having their stories shared on Tor social media / comms / in a public way. Right now, the Tor Stories survey (https://survey.torproject.org/index.php/7719420) has the language below, but @duncan suggests that the uX team would "like to start asking for consent to use quotes in general UX surveys too – however in those cases it should be an optional question at the end of the survey so it doesn't prevent users from participating entirely."

Here's what's currently in the Tor Stories survey:

We want to know how you learned about Tor and how Tor has helped you.

The more details we have, the easier it can be for us to present our value to possible donors and funders. With more funding, we can make Tor even better for you and other people around the world.

Your responses may be shared on social media and in Tor promotional materials. Please share as much as possible without putting yourself at risk.