Is your feature request related to a problem? Please describe.
Develop a Fastly plugin for the OpenCost Plugins ecosystem

Additional context
Fastly billing APIs available here: https://www.fastly.com/documentation/reference/api/account/billing/

Example PR with an implemented Plugin: #41
This issue qualifies for our bounty program, read more details here: https://www.opencost.io/blog/introducing-opencost-plugins