Add a separate CONTRIBUTING.md file

Hopefully provides a /little/ more information about the build process.
Hey, also means I only need to add a CoC to complete GH's community tab!

In all seriousness, there's probably a lot more I need to flesh out
here, such as some kind of vision and guides for issues/PRs. But this at
least documents the local development process. Somewhat.

CONTRIBUTING.md

@@ -0,0 +1,36 @@
+# Contributing to CC: Tweaked
+As with many open source projects, CC: Tweaked thrives on contributions from other people! This document (hopefully)
+provides an introduction as to how to get started in helping out.
+
+If you've any other questions, [just ask the community][community] or [open an issue][new-issue].
+
+## Reporting issues
+If you have a bug, suggestion, or other feedback, the best thing to do is [file an issue][new-issue]. When doing so,
+do use the issue templates - they provide a useful hint on what information to provide.
+
+## Developing
+In order to develop CC: Tweaked, you'll need to download the source code and then run it. This is a pretty simple
+process.
+
+ - **Clone the repository:** `git clone https://github.com/SquidDev-CC/CC-Tweaked.git && cd CC-Tweaked`
+ - **Setup Forge:** `./gradlew setupDecompWorkspace`
+ - **Run Minecraft:** `./gradlew runClient` (or run the `GradleStart` class from your IDE).
+
+If you want to run CC:T in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from `build/libs`.
+These commands may take a few minutes to run the first time, as the environment is set up, but should be much faster
+afterwards.
+
+### Code linters
+CC: Tweaked uses a couple of "linters" on its source code, to enforce a consistent style across the project. While these
+are run whenever you submit a PR, it's often useful to
+
+ - **[Checkstyle]:** Checks Java code to ensure it is consistently formatted. This can be run with `./gradlew build` or
+   `./gradle check`.
+ - **[illuaminate]:** Checks Lua code for semantic and styleistic issues. See [the usage section][illuaminate-usage] for
+   how to download and run it.
+
+[new-issue]: https://github.com/SquidDev-CC/CC-Tweaked/issues/new/choose "Create a new issue"
+[community]: README.md#Community "Get in touch with the community."
+[checkstyle]: https://checkstyle.org/
+[illuaminate]: https://github.com/SquidDev/illuaminate/
+[illuaminate-usage]: https://github.com/SquidDev/illuaminate/blob/master/README.md#usage

README.md

@@ -37,20 +37,14 @@ ## Relation to CCTweaks?
 computers.
 
 ## Contributing
-Any contribution is welcome, be that using the mod, reporting bugs or contributing code. In order to start helping
-develop CC:T, you'll need to follow these steps:
-
- - **Clone the repository:** `git clone https://github.com/SquidDev-CC/CC-Tweaked.git && cd CC-Tweaked`
- - **Setup Forge:** `./gradlew setupDecompWorkspace`
- - **Test your changes:** `./gradlew runClient` (or run the `GradleStart` class from your IDE).
-
-If you want to run CC:T in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from `build/libs`.
+Any contribution is welcome, be that using the mod, reporting bugs or contributing code. If you want to developing the
+mod, [check out the instructions here](CONTRIBUTING.md#developing).
 
 ## Community
 If you need help getting started with CC: Tweaked, want to show off your latest project, or just want to chat about
-ComputerCraft we have a [forum](https://forums.computercraft.cc/) and [Discord guild](https://discord.gg/H2UyJXe)!
-There's also a fairly populated, albeit quiet [IRC channel](http://webchat.esper.net/?channels=#computercraft), if
-that's more your cup of tea.
+ComputerCraft we have a [forum](https://forums.computercraft.cc/) and [Discord guild](https://discord.computercraft.cc)!
+There's also a fairly populated, albeit quiet [IRC channel](http://webchat.esper.net/?channels=computercraft), if that's
+more your cup of tea.
 
 I'd generally recommend you don't contact me directly (email, DM, etc...) unless absolutely necessary (i.e. in order to
 report exploits). You'll get a far quicker response if you ask the whole community!