Fill out a README (#26)

Author: alexcrichton

README.md

@@ -1,8 +1,46 @@
 # `wasm-component-ld`
 
-A work-in-progress and/or proof-of-concept linker which wraps `wasm-ld` and then
-executes `wit-component` to produce a component output instead of a core wasm
-output. Intended for the upcoming `wasm32-wasip2` target in the Rust compiler.
+This crate contains a binary named `wasm-component-ld` which is a wrapper around
+two pieces of functionality used to produce a [WebAssembly Component]
+
+1. The `wasm-ld` linker driver provided by LLVM
+2. The [`wit_component::ComponentEncoder`] type
+
+This binary will first invoke `wasm-ld` and then run the componentization
+process to produce a final component.
+
+[WebAssembly Component]: https://component-model.bytecodealliance.org/
+[`wit_component::ComponentEncoder`]: https://docs.rs/wit-component/latest/wit_component/struct.ComponentEncoder.html
+
+## Installation
+
+This repository provides [precompiled
+binaries](https://github.com/bytecodealliance/wasm-component-ld/releases) of
+`wasm-component-ld`. This repository can also be installed with [`cargo binstall`].
+
+Installations of [wasi-sdk] have this binary packaged by default in the sysroot
+and the Rust `wasm32-wasip2` target, upon reaching tier 2, will also come
+packaged with this binary included.
+
+This means that while a version can be installed manually it should not be
+required to do so.
+
+[`cargo binstall`]: https://github.com/cargo-bins/cargo-binstall
+[wasi-sdk]: https://github.com/WebAssembly/wasi-sdk
+
+## Options
+
+The `wasm-component-ld` binary is suitable to use as a linker driver during
+compilations. For Clang and Rust the `wasm32-wasip2` target will automatically
+invoke this binary as the linker.
+
+This means that `wasm-component-ld` forwards most of its arguments to `wasm-ld`.
+Additionally all flags of `wasm-ld` are supported and forwarded to `wasm-ld`.
+For example you can invoke the linker like `wasm-component-ld --max-memory=N
+...`.
+
+The `wasm-component-ld` binary has a few custom arguments for itself as well
+which are not forwarded to `wasm-ld` and can be explored with `-h` or `--help`.
 
 # License