Added GitHub Issue and PR templates.

.github/ISSUE_TEMPLATE.md

+<!-- You can erase any parts of this template not applicable to your issue. -->
+
+### Description
+
+[Description of the bug or feature]
+
+## Steps to Reproduce the Problem
+
+  1.
+  2.
+
+**Expected behavior:** [What you expected to happen]
+
+**Actual behavior:** [What actually happened]
+
+## Specifications
+
+  - Version:  (You can get this information from executing `ogs --version`)
+  - Platform: (Operating System)

.github/PULL_REQUEST_TEMPLATE.md

+<!-- You can erase any parts of this template not applicable to your Pull Request. -->
+
+Fixes # <!-- you may add issues here to automatically close them -->
+
+1. [ ] Tests covering your feature were added?
+2. [ ] Any new feature or behavior change was documented?