Fill in readme and user documentation

[alexeagle]

Currently it's a mystery what is the value prop, and how to adopt and use this repo.

rules_js and rules_py READMEs are a place to start - and we need high-level documentation as well.

[derived-coder]

Is there a fully documented example from start? Would be nice to see it in the main readme.

[Warchant]

I'd write one by myself, but I am unable to use this toolchain at all... I am using bazel 5.3.0

ERROR: error loading package '': Every .bzl file must have a corresponding package, but '@hermetic_gcc_linux//toolchain:repositories.bzl' does not have one. Please create a BUILD file in the same or any parent directory. Note that this BUIL

http_archive(
    name = "hermetic_gcc_linux",
    urls = [
        "https://github.com/aspect-build/gcc-toolchain/archive/refs/tags/0.4.2.zip"
    ],
    sha256 = ""
)
load("@hermetic_gcc_linux//toolchain:repositories.bzl", "gcc_toolchain_dependencies")
gcc_toolchain_dependencies()

load("//:internal.bzl", "internal_dependencies")

internal_dependencies()

load("@rules_pkg//:deps.bzl", "rules_pkg_dependencies")

rules_pkg_dependencies()

load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")

bazel_skylib_workspace()

load("@aspect_bazel_lib//lib:repositories.bzl", "aspect_bazel_lib_dependencies")

aspect_bazel_lib_dependencies()

load("@hermetic_gcc_linux//toolchain:defs.bzl", "gcc_register_toolchain", "ARCHS")
gcc_register_toolchain(
    name = "gcc_toolchain_x86_64",
    sysroot_variant = "x86_64-X11",
    target_arch = ARCHS.x86_64,
)