Finalize docs structure and preliminary content

### References

- https://docs.dev.to/
- https://stripe.com/docs/api

### Helpers

- https://vuepress.vuejs.org/guide/basic-config.html
- https://home.aveek.io/blog/post/build-a-documentation-site-with-vuepress/
- https://www.digitalocean.com/community/tutorials/how-to-build-a-documentation-system-with-vue-and-vuepress
- https://vuepressbook.com/introduction.html