More emphasize on using <Formik /> instead of useFormik in tutorial.md

[sepans]

I was using Formik for the first time and I landed on the tutorial page and without reading the docs properly I copied the first code snippet (I tend to beleive I am not the only person doing this 🤦🏽 ) So ended up with an annoying bug with the cursor:

Screenshots

It turned out I just had to use <Formik /> instead of useFormik in the first basic example.

Now that I understand the structure of the docs I appreciate how it describes the underlying structure but I wish there was a more attention-grabbing alert to point newbie users to a real 'basic' example.

Thank you ❤️