docs: Add "getting-started"

from the Wiki that details how to get started with using `cross`.

README.md

@@ -36,8 +36,8 @@ New contributors are welcome! Please join our [Matrix room] and say hi.
 
 ## Dependencies
 
-See our [Getting Started](https://github.com/cross-rs/cross/wiki/Getting-Started) guide
-for detailed installation instructions.
+See our [Getting Started](./docs/getting-started.md) guide for detailed
+installation instructions.
 
 - [rustup](https://rustup.rs/)
 

docs/getting-started.md

@@ -0,0 +1,123 @@
+<!--toc:start-->
+- [Installing Cross](#installing-cross)
+    - [Installing Rust via Rustup](#installing-rust-via-rustup)
+    - [Installing Cross](#installing-cross)
+- [Installing A Container Engine](#installing-a-container-engine)
+- [Cross-Compiling Your First Package](#cross-compiling-your-first-package)
+<!--toc:end-->
+
+New to cross? Cross-compilation? Container engines? Here's how to get up-and-running.
+
+# Installing Cross
+
+## Installing Rust via Rustup
+
+`cross` requires a `rustup` installation of Rust. To do so, the recommended
+instructions are documented [here](https://www.rust-lang.org/tools/install),
+but might differ on some platforms. For UNIX-like systems, run the following
+command in a terminal and follow the instructions to install Rust and add Rust
+to the path:
+
+```bash
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+```
+
+On Windows, download
+[rustup-init.exe](https://static.rust-lang.org/rustup/dist/i686-pc-windows-gnu/rustup-init.exe)
+or following the [other installation
+methods](https://forge.rust-lang.org/infra/other-installation-methods.html),
+say, to install from a package manager.
+
+On some platforms, such as NixOS, you might need to use a package manager since
+the default `rustup` install will fail. On NixOS, you should run the following,
+which will install `rustup` and the latest `stable` release of Rust.
+
+```bash
+nix-env -i rustup
+rustup toolchain install stable
+```
+
+Note that you might need additional tools on some platforms to get `rustc` and
+`cargo` working. On UNIX-like systems, this generally means an install of GCC
+or Clang. For example, on NixOS you will likely need to install GCC via
+`nix-env -i gcc` and then go into a GCC and Rust shell (`nix-shell -p gcc
+rustup`). On Alpine, you'll need to run `apk add libgcc gcc musl-dev`. Exact
+instructions will differ by OS and Linux distro, feel free to ask on the
+[discussion](https://github.com/cross-rs/cross/discussions) or our [Matrix
+room](https://matrix.to/#/#cross-rs:matrix.org) if you have any questions.
+
+
+## Installing Cross
+
+Once `cargo` is installed via `rustup`, and the necessary additional tools are
+present, you can now install `cross` via `cargo`:
+
+```bash
+cargo install cross
+# Optionally, if you have cargo-binstall, you can install via pre-built binary
+cargo binstall cross
+```
+
+Once `cross` is installed, you need a container engine and you can start
+cross-compiling.
+
+
+# Installing A Container Engine
+
+On Windows and macOS, we generally recommend you use Docker unless you know
+what you're doing. [Docker
+Desktop](https://www.docker.com/products/docker-desktop/) install instructions
+can be found [here](https://www.docker.com/products/docker-desktop/). On Linux,
+you can either install via [Docker
+Engine](https://docs.docker.com/engine/install/ubuntu/), [Docker
+Desktop](https://docs.docker.com/desktop/install/linux-install/) or
+[Podman](https://podman.io/getting-started/installation). We generally
+recommend Podman, since it runs rootless by default. If you choose to use
+Docker, make sure you add users to the [docker
+group](https://docs.docker.com/engine/install/linux-postinstall/#manage-docker-as-a-non-root-user)
+so it can be run without `sudo` (note that this has security implications) or
+use [rootless](https://docs.docker.com/engine/security/rootless/)<sup>†</sup>
+Docker.
+
+If you use Docker Desktop for Windows, ensure you're using the WSL2. Follow the
+[WSL2 installation
+instructions](https://docs.microsoft.com/en-us/windows/wsl/install) to enable
+the [WSL2 backend in docker](https://docs.docker.com/desktop/windows/wsl/).
+
+Once your container engine is installed, you can check that it is running via:
+
+```bash
+# or use podman, if installed
+$ docker ps -a
+```
+
+<sup>†</sup>Using rootless docker also requires setting the environment
+variable `CROSS_ROOTLESS_CONTAINER_ENGINE=1`.
+
+
+# Cross-Compiling Your First Package
+
+Once both `cross` and the container engine are installed, you can build your
+first package: this is all that's required.
+
+```bash
+$ cargo init --bin hello
+$ cd hello
+$ cross run --target aarch64-unknown-linux-gnu
+   Compiling hello v0.1.0 (/project)
+    Finished dev [unoptimized + debuginfo] target(s) in 0.64s
+     Running `/linux-runner aarch64 /target/aarch64-unknown-linux-gnu/debug/hello`
+Hello, world!
+```
+
+This will automatically install the Rust target required and the Docker image
+containing the toolchain to cross-compile your target.
+
+If you get an error similar to `error: toolchain
+'stable-x86_64-unknown-linux-gnu' does not support components`, try
+reinstalling that toolchain with rustup.
+
+```sh
+$ rustup toolchain uninstall stable-x86_64-unknown-linux-gnu
+$ rustup toolchain install stable-x86_64-unknown-linux-gnu --force-non-host
+```