chore(docs): add nix installation instructions

Summary: This should work for just about everyone OOTB I think, but putting this
out early to make sure any nits are found early on.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Change-Id: I0710a637b94abad2a433abd310e68395

Author: thoughtpolice

docs/00-START-HERE.md

@@ -1,3 +1,81 @@
 # 00 — Starting Line: installing Nix and playing around
 
-Lorem in aliquip cupidatat cupidatat est mollit...
+Let's go ahead and install Nix. To do that, we'll use the
+**[nix-installer tool]** by Determinate Systems. This works on many platforms,
+but most importantly it works on **aarch64 Linux** and **x86_64 Linux**. Use the
+following command in your shell, **it should work on any Linux distro of your
+choice**:
+
+[nix-installer tool]: https://github.com/DeterminateSystems/nix-installer
+
+```bash
+curl \
+  --proto '=https' --tlsv1.2 \
+  -sSf -L https://install.determinate.systems/nix \
+| sh -s -- install
+```
+
+After you do this, **you must log in and log back out of your desktop
+environment** to get a new login session. This is so that your shell can have
+the Nix tools installed on `$PATH` and so that your user shell can see some
+extra settings.
+
+You should now be able to do something like the following; try running these
+same commands on your machine:
+
+```
+$ nix --version
+nix (Nix) 2.16.1
+```
+
+```
+$ nix run nixpkgs#nix-info -- -m
+ - system: `"x86_64-linux"`
+ - host os: `Linux 5.15.90.1-microsoft-standard-WSL2, Ubuntu, 22.04.2 LTS (Jammy Jellyfish), nobuild`
+ - multi-user?: `yes`
+ - sandbox: `yes`
+ - version: `nix-env (Nix) 2.16.1`
+ - channels(root): `"nixpkgs"`
+ - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixpkgs`
+```
+
+If the above worked, you're now cooking with gas!
+
+> _**NOTE**_: While there is an upstream tool to install Nix, written in Bash,
+> we use the Determinate Systems installer — which will hopefully replace the
+> original — because it's faster, and takes care of several extra edge cases
+> that the original one couldn't handle, and makes several changes to the
+> default installed configuration to make things more user friendly. Determinate
+> Systems is staffed by many long-time Nix contributors and the creator of Nix,
+> and is trustworthy.
+
+## Do some fun stuff
+
+One of the best things about Nix that requires _very little_ knowledge of it is
+that it lets you install the latest and greatest versions of many tools _on any
+Linux distribution_. We'll explain more about that later on. But just as a few
+examples:
+
+- **Q**: I want the latest version of Deno. Can we get that?
+- **A**: `nix profile install nixpkgs#deno`, and you're done!
+
+<!-- break bulletpoints -->
+
+- **Q**: What about HTTPie? A nice Python application?
+- **A**: Same idea: `nix profile install nixpkgs#httpie`
+
+<!-- break bulletpoints -->
+
+- **Q**: What about my favorite Rust applications, like ripgrep and bat?
+- **A.1**: `nix profile install nixpkgs#ripgrep`
+- **A.2**: `nix profile install nixpkgs#bat`
+- **A.3**: And yes, you also have exa, fd, hyperfine, and more!
+
+<!-- break bulletpoints -->
+
+- **Q**: What does '`nixpkgs`' mean? And how can I find out more?
+- **A**: Please keep reading...
+
+## Next page
+
+TODO FIXME (aseipp): implement