Updating the readme doc (#70)

Updating to add additional steps for building as well as options for testing dev releases.

Author: black2d

README.md

@@ -8,7 +8,7 @@ The JS Compute Runtime for Fastly's [Compute@Edge platform](https://www.fastly.c
 
 Note that this repository uses Git submodules, so you will need to run
 
-```
+```sh
 git submodule update --recursive --init
 ```
 
@@ -21,13 +21,63 @@ To build from source, you need to ensure that the headers and object files for t
 (cd c-dependencies/spidermonkey && sh download-engine.sh)
 ```
 
+
 Alternatively, the engine can also be built from source using `c-dependencies/spidermonkey/build-engine.sh`. That should only be required if you want to modify the engine itself, however.
 
+In additon you need to have the following tools installed to successfully build, and build from a linux based system.
+
+- Rust 
+  ```
+  curl -so rust.sh https://sh.rustup.rs && sh rust.sh -y
+  restart shell or run source $HOME/.cargo/env
+  ```
+- Build tools
+  ```sh
+  sudo apt install build-essential
+  ```
+- binaryen
+  ```sh
+  sudo apt install binaryen
+  ```
+- rust target wasm32-wasi
+  ```sh
+  rustup target add wasm32-wasi
+  ```
+- cbindgen
+  ```sh
+  cargo install cbindgen
+  ```
+- wasi-sdk
+  ```sh
+  curl -sS -L -O https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-12/wasi-sdk-12.0-linux.tar.gz
+  tar xf wasi-sdk-12.0-linux.tar.gz
+  sudo mkdir -p /opt/wasi-sdk
+  sudo mv wasi-sdk-12.0/* /opt/wasi-sdk/
+  ```
+- rust version - the rust version may need to be pinned due to the WASI spidermonkey version, the current version can be found at [main.yml](.github/workflows/main.yml) under "Install pinned Rust version and wasm32-wasi target"
+  ```
+   rustup update 1.57.0 --no-self-update
+   rustup default 1.57.0
+  ```
+
 Once that is done, the runtime and the CLI tool for applying it to JS source code can be built using cargo:
 ```sh
 cargo build --release
 ```
 
+#### Build a windows executable
+To build for windows on a linux system you need to install the following modules:
+
+```
+sudo apt-get install gcc-mingw-w64
+rustup target add x86_64-pc-windows-gnu
+```
+
+then you can run the following
+```sh
+cargo build --target x86_64-pc-windows-gnu --release
+```
+
 ## Testing
 
 The JS Compute Runtime doesn't currently contain automated tests itself. Instead, Fastly runs an automated test suite for an internal repository for the JavaScript SDK using the runtime.
@@ -43,6 +93,20 @@ addEventListener('fetch', e => {
   console.log("Hello World!");
 });
 ```
+Create a fastly.toml file which is required for the application to run:
+```toml
+# This file describes a Fastly Compute@Edge package. To learn more visit:
+# https://developer.fastly.com/reference/fastly-toml/
+
+authors = ["[email protected]"]
+description = "test service"
+language = "javascript"
+manifest_version = 2
+name = "test"
+service_id = ""
+
+```
+
 into a C@E service with your build of the CLI tool, run the following command:
 ```sh
 cargo run --release -- test.js test.wasm
@@ -52,3 +116,10 @@ Then test your service in Viceroy:
 ```sh
 viceroy test.wasm
 ```
+
+## Testing a Dev Release
+:warning:	**You should not use this for production workloads!!!!!!!!**
+
+Dev builds are released before production releases to allow for further testing. These are not released upstream to NPM, however you can acquire them from the [Releases](https://github.com/fastly/js-compute-runtime/releases/) section. Download the runtime for your platform, extract the executable and place it in the /node_modules/@fastly/js-compute/bin/PLATFORM folder of your Compute@Edge project. Then you can use the normal [Fastly CLI](https://github.com/fastly/cli) to build your service. 
+
+Please submit an [issue](https://github.com/fastly/js-compute-runtime/issues) if you find any problems during testing.