Update and re-organize FT example

[gagdiez]

Background

This repository contains the "official" FT example, but currently it is very outdated - uses an old version of NAJ - and the folder organization does not follow our canonical examples (e.g. hello world)

User Story

As a user I would like to have the most updated version on how an base FT smart contract looks like

Acceptance Criteria

• The updated version uses the latest version of NEAR SDK RS (5.5)
• The updated version has the same folder organization as our Hello World example

Resources & Additional Notes

• Hello World example

Priority

• 🟠 P1 : High