Add issue templates

I'm not entirely a fan of massive templates, but there's 
been a couple of lacklustre issues recently, so it's probably
good to formalise my guidelines.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,16 @@
+---
+name: Bug report
+about: Report some misbehaviour in the mod
+
+---
+
+<!--
+## Before reporting
+ - Search for the bug both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+)
+ - If possible, try to reproduce on vanilla ComputerCraft. If it still occurs, [report on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new) instead.
+-->
+
+## Useful information to include:
+ - Minecraft version
+ - CC: Tweaked version
+ - Detailed reproduction steps!** Sometimes I can spot a bug pretty easily, but often it's much more obscure. Anything you can give which will help reproduce it means it'll get fixed quicker.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,15 @@
+---
+name: Feature request
+about: Suggest an idea or improvement
+
+---
+
+<!--
+## Before reporting
+ - Search for the suggestion both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+). It's possible someone's suggested it before!
+ - Unless something is specific to CC:Tweaked, try to [suggest them on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new). There's a lot more people watching it, so it allows the wider community to contribute.
+-->
+
+## Useful information to include:
+ - Explanation of how the feature/change chould work.
+ - Some rationale/use case for a feature. I'd like to keep CC:T as minimal