Introduce a CI job that validates RFCs

[mohammadfawaz]

We can start with a simple lint check like the one we run in https://github.com/FuelLabs/fuel-specs and we can expand to something more substantial like https://github.com/ethereum/eip_validator

[adlerjohn]

https://github.com/DavidAnson/markdownlint

[adlerjohn]

https://github.com/github/super-linter should be a usable action to run markdownlint

[adlerjohn]

https://github.com/FuelLabs/fuel-indexer/blob/848f3438eccc1c111da23772ab5f8205348fb86e/.github/workflows/ci.yml#L222-L227