add toc to 2018 archive

2018.md

@@ -1,7 +1,49 @@
 # Awesome Advent of Code
 
-This file contains the archived list of solutions to the 2018 Advent
-of Code event.
+This file contains the archived list of solutions to the 2018 [Advent
+of Code] event.
+
+[Advent of Code]: https://adventofcode.com/
+
+* [2018](#2018)
+  * [Solutions](#solutions)
+    * [AWK](#awk)
+    * [Ada](#ada)
+    * [Bash](#Bash)
+    * [C](#c)
+    * [C#](#c-1)
+    * [C++](#c-2)
+    * [Clojure](#clojure)
+    * [Crystal](#crystal)
+    * [Dart](#dart)
+    * [Elixir](#elixir)
+    * [Elm](#elm)
+    * [F#](#f)
+    * [Go](#go)
+    * [Groovy](#groovy)
+    * [Haskell](#haskell)
+    * [Idris](#idris)
+    * [Java](#java)
+    * [JavaScript](#javascript)
+    * [Julia](#julia)
+    * [Kotlin](#kotlin)
+    * [Nim](#nim)
+    * [OCaml](#ocaml)
+    * [PHP](#php)
+    * [Perl](#perl)
+    * [Pony](#pony)
+    * [PowerShell](#powershell)
+    * [Python](#python)
+    * [Racket](#racket)
+    * [ReasonML](#reasonml)
+    * [Red](#red)
+    * [Ruby](#ruby)
+    * [Rust](#rust)
+    * [Scala](#scala)
+    * [Swift](#swift)
+    * [TypeScript](#typescript)
+    * [Zig](#zig)
+  * [Live Streams](#live-streams)
 
 ## 2018