github: Add issue templates

[skip ci]

Closes #965

Co-authored-by: Daniel Stokes <kupomail@gmail.com>

.github/ISSUE_TEMPLATE/bug.md

@@ -0,0 +1,25 @@
+---
+name: Bug report
+about: Report a defect
+title:
+labels:
+assignees:
+---
+
+## Description
+<!-- Provide a clear and concise description of the bug: what you expected to
+     happen, and what actually happened instead.  If you have a log file or
+     crash report, please attach those! -->
+
+## Steps to Reproduce
+<!-- The most minimal but complete set of steps to reproduce the bug, with a
+     code snippet that clearly demonstrates the bug.  We must be able to run
+     the code, ie. you must include any required assets. -->
+
+## Environment
+ * Operating system:
+ * System architecture:
+ * Panda3D version: <!-- import panda3d; print(panda3d.__version__) -->
+ * Installation method: (eg. pip, wheel, SDK, built from source)
+ * Python version (if using Python):
+ * Compiler (if using C++):

.github/ISSUE_TEMPLATE/enhancement.md

@@ -0,0 +1,15 @@
+---
+name: Enhancement request
+about: Request new functionality or improvement to existing functionality
+title:
+labels: enhancement
+assignees:
+---
+
+## Description
+<!-- Please clearly describe which change you want to be made. -->
+
+## Use Case
+<!-- Describe why you need this change, how it will help you, including any
+     other imagined scenarios in which it will be useful.  If this request is
+     urgent and you have no alternatives, please state so as well. -->