Use full names for payload object

[vitonsky]

Check the docs https://plausible.io/docs/events-api and replace short property names to its full name version for consistency and avoid confusion.

Currently it is not clear how to pass window dimensions. Docs have no info about props like width or height

It's because the reference package is uses short names for payload object:

https://github.com/plausible/plausible-tracker/blob/ab75723ad10660cbaee3718d1b0a670e2dfd717d/src/lib/request.ts#L65-L73

It would be nice to test with CURL that we can replace short names to full names, and if it will works fine, leave full names, since it's more verbose and don't confuse everyone.

It is task for another issue although.

Originally posted by @vitonsky in #24 (comment)