* upgrades LLVM to v14
* migrates from the unmaintained `action-rs/*` actions to [dtolnay/rust-toolchain](https://github.com/dtolnay/rust-toolchain), using [Swatinem/rust-cache](https://github.com/Swatinem/rust-cache/) as a cache layer.
* adds a cache layer for LLVM build
* adds a weekly cron schedule for all workflows
* fixes an issue in the docblocks
* Allowlist types generated by bindgen
Tidied up build script as well, layout tests are no longer generated
unless `EXT_PHP_RS_TEST` env variable is set. Much quicker build times
and smaller output size.
* Fix build
* Override Rust toolchain when running CI
* Started work on guide, added types
* Rewrite argument parser to allow referencs
Primarly so that `&str` is a valid parameter type.
* Remove generic `Into<String>` conversion to exception
* Worked on guide, added macros
* Build guide when building docs
* Allow manual trigger of docs build
* `cargo fmt`