add PR and issue templates

Author: alperaltuntas

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,10 @@
+### Description of the issue:
+
+### Version:
+- CESM: [version]
+- POP2: [version]
+
+### Machine/Environment Description:
+
+### Any xml/namelist changes or SourceMods:
+

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+### Description of changes:
+
+[ Description of the changes in this Pull Request. It should be enough
+information for someone not following this development to understand.]
+
+### Testing:
+ 
+Test case/suite:
+Test status: [bit for bit, roundoff, climate changing]
+
+Fixes [POP2 Github issue #]
+
+User interface (namelist or namelist defaults) changes?
+