The "Suggested Workflow" documentation is out-of-date

[Xophmeister]

Describe the bug
In the README, the "Suggested Workflow" documentation no longer corresponds with what needs to be done to, e.g., add a new language. It also refers to relics that we no longer use (e.g., (#language!) pragma).

To Reproduce
Read the README.

Expected behaviour
The README should be aligned with the state of the code.

Environment

• OS name + version: NixOS 23.05
• Version of the code: 79b9352

Additional context
Given the significant changes being made in #643, which are directly related to this issue, any fix should probably wait for this PR (or, better yet, be incorporated into the PR).