Branding, subscription and donation tweaks

@alicewilliams36 and I thought it would be most useful if we bundled these all into one ticket, as they all involve tinkering with similar areas.

Basic aims:

To ensure it's obvious the service comes from mySociety, in every part of the user journey including confirmation emails etc
To refine the wording of donation prompts
To encourage sign-ups to our newsletter

All emails

(confirm send/confirm reminder/failure/questionnaire/questionnaire reminder/any others)

[ ] At the moment there's a WriteToThem logo at the top. Can we add the same mySociety banner that's on the homepage, 'A service from mySociety'?

Footer of website

[ ] Please change the donation request wording from "Your donations keep this site and others like it running" to:

This site is not publically funded. Donate today to help everyone engage in democracy.

[ ] Can we add a mailout sign-up?

Stay updated on mySociety's projects ... or choose what you'd like to hear about with a link to https://mysociety.us9.list-manage.com/subscribe?u=53d0d2026dea615ed488a8834&id=287dc28511

Success screens

Apologies that I can't remember how to see what these look like at the moment, but we'd like the same subscribe and donation prompts as above to appear on the screens that indicate a success, ie:

[ ] Your message is on its way
[ ] 'Yes' to the 'did you get a reply' survey

I assume these pages also have the current WTT banner with the mySociety pennant on it - but if they don't for any reason, can we add it?

I hope that all makes sense!

mysociety / writetothem