Update post-submission message

[mjumbewu]

• [x] For Demographic survey, put placeholder text in submission popup: "Thank you for your submission. Please help us answer this optional survey." Add this before the how to stay involved. OPB will send final link.
• [x] Reduce the size of the how to stay involved.
• [x] Use the "this optional survey" text as the link title for demographic survey
• [x] Add link for demographic survey placeholder
• [x] Add link for mailing list placeholder ("Sign up for the newsletter" with https://www.boston.gov/departments/participatory-budgeting#newsletter)

[mjumbewu]

Use the following links for each language:

• English: https://www.surveymonkey.com/r/ideasinactionsurvey1
• Simplified Chinese: https://www.surveymonkey.com/r/ideasinactionsurvey1?lang=zh_Hans
• Haitian Creole: https://www.surveymonkey.com/r/ideasinactionsurvey1?lang=fr_HT
• Brazilian Portuguese: https://www.surveymonkey.com/r/ideasinactionsurvey1?lang=pt_BR
• Spanish: https://www.surveymonkey.com/r/ideasinactionsurvey1?lang=es
• Vietnamese: https://www.surveymonkey.com/r/ideasinactionsurvey1?lang=vi

See https://www.boston.gov/departments/participatory-budgeting for the format of the links.