Add shell.nix for Nix(OS) users (#18)

This adds a shell.nix file for Nix(OS) users. In Nix, a shell.nix file is used to create a development environment with certain packages installed, in this case just Go.

.github/workflows/tangle.yml

@@ -3,6 +3,7 @@ on:
   - push
   - pull_request
 
+
 env:
   FILES: 'Implementation.md WhitespacePreservation.md SubdirectoryFiles.md LineNumbers.md IndentedBlocks.md'
   GOVER: '^1.16'

Implementation.md

@@ -1,7 +1,7 @@
 # lmt - literate markdown tangle
 
 This file implements a tangle program for a literate programming style
-where the code is weaved into markdown code blocks. There is no corresponding
+where the code is tangled from markdown code blocks. There is no corresponding
 weave, because the markdown itself can already be read as the documentation,
 either through a text editor or through an online system that already renders
 markdown such as GitHub.

Nix-Shell.md

@@ -0,0 +1,18 @@
+# About Nix
+Nix is a package manager designed to allow for completely reproducible builds. It allows for developers to have reproducible build environments in order to ensure consistency. For more information, see <https://nixos.org/>.
+
+# Nix Shell
+Nix development shells can be used to get development environments which can be accessed using the `nix-shell` command.
+
+Firstly, we must define a function. Nix expressions are written in a functional language (also called Nix) and use the function as their basic unit. This one takes a parameter called `pkgs` with a default value of the primary Nix package collection.
+```nix shell.nix+=
+{ pkgs ? import <nixpkgs> {} }:
+```
+
+Now, we can create a shell using the `pkgs.mkShell` function. This function creates the shell that will be accessed and defines properties of it. In our case, we use the `buildInputs` parameter to include our build dependencies (ie. Golang) in this shell.
+```nix shell.nix+=
+pkgs.mkShell {
+  buildInputs = with pkgs; [ go ];
+}
+```
+

README.md

@@ -24,6 +24,9 @@ directory. You can use the `-o $path` argument to `go build` to build
 the binary in a different location. (i.e. `go build -o ~/bin/` to put the
 binary in `~/bin/`.)
 
+#### A note for Nix(OS) users
+This repo also comes with a `shell.nix` file. While an existing version is included, like lmt itself, this is mainly for bootstrapping purposes. To compile it, use `lmt Nix-Shell.md`
+
 ## Demo
 
 To observe `lmt` at work, put this file in an empty directory, cd to that

shell.nix

@@ -0,0 +1,4 @@
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.mkShell {
+  buildInputs = with pkgs; [ go ];
+}