Make feedback form functional (serverless)

[csobrien90]

This issue is addressed - there is now a functioning feedback form! I'm going to leave this open, though, and retag because the final, pending part of this is to write documentation. Here are some relevant links to assist in that:

• https://github.com/csobrien90/bb-feedback-function
• https://github.com/csobrien90/bb-admin-dashboard
• https://github.com/csobrien90/band-book/commit/c43f0f6661374a08e3efe7401af8915b6217d132
• https://github.com/csobrien90/band-book/commit/0fda01588d79e0f0e6815c3fa337ef5846e35001