Add docs generation

[zec]

As a crate which isn't being released on crates.io currently, we don't just get online docs for free from docs.rs. Hand-maintaining generation is tedious and prone to errors of omission; as such, we should probably set up a GitHub workflow for building the docs upon an update of the main branch, generating the HTML and pushing it onto the gh-pages branch.

[zec]

...and even if we do end up releasing this on crates.io (which I'd be more amenable to if we figure out a solution to #1), we wouldn't be able to rely on docs.rs to generate our Rustdocs for us, as we rely on cFE and OSAL headers being available.