I'd like to use this issue as a tracking issue for filling out gaps in wasmtime's introductory documentation. This includes our book (rendered), API documentation (rendered), and [examples](https://github.com/bytecodeallianc

This needs to be handled in the object write code (driver/aot.rs) and the archive build code (archive.rs). It should be fine to use sess.fatal on an error during writing of a file.

Taken from #37:

• there are a few links to an old version of the cranelift-module crate, for Module and Backend for instance.
• ditto for cranelift-frontend
• integer constants is linking to the readthedocs documentation, which is out of date. We should instead link to the IR descriptions (that live here).
• the links to line numbers of the example programs foo and iterative_fib are off by o