add lemon squeezy as payment provider

[vincanger]

Resolves #103 and Resolves #16

• [x] Add lemonsqueezy checkout (operation, util functions, etc)
• [x] Add webhook and handle necessary events
• [x] Add operations to pricing page
• [x] Add ability to access lemonsqueezy customer portal after user pays
  • [x] on Pricing Page
  • [x] on Account Page
• [x] Test one-time payment product
• [x] add lemonsqueezy analytics methods
• [x] update app_diff
• [x] Add docs

when deploying, make sure to:

• [x] change stripe webhook url payments-webhook
• [x] update product plan id env vars

Note: when developing with webhooks locally, use ngrok and create a tunnel to server on port 3001. Add the url it provides you + /lemonsqueezy-webhook to your webhook settings on the lemonsqueezy dashboard e.g. 9bbf-176-199-209-145.ngrok-free.app/lemonsqueezy-webhook:

ngrok http 3001

[aiddroid]

Please reactor this into a common payment interface.