feat: Update to use "new" Integrations

[nmsturcke]

Sentry no longer allows for the creation of (now legacy) webhooks. Or rather... it does, but it's incredibly hidden and convoluted.

This PR:

• Updates the API to use the "new" Sentry Integrations, while maintaining support for legacy webhooks
• Updates /create to explain how to use the "new" Sentry Integrations, I also included the same demo from the Sentry Docs. I'm not sure whether this is (legally?) okay, but I feel it does make it a lot easier to understand.
• Fixes Not working? 500s #48 and potential similar issues/confusion
• Removes the "Data Loss Notification" warning SVG added in e2c5c7e, that was not removed when the text was removed in 2a460fb
• Updates the native integration "Common Question" to address its existence for paid plans only