Created `PULL_REQUEST_TEMPLATE.md` and `ISSUE_TEMPLATE.md`

[ansrivas]

Proposed changes in this pull request

This pull request introduces a template for creating pull-requests and issues on github repository of UNetwork.

Type (put an x where ever applicable)

• [ ] Bug fix: Link to the issue
• [ ] Feature (Non-breaking change)
• [ ] Feature (Breaking change)
• [x] Documentation Improvement

Checklist

Please put an x against the checkboxes. Write a small comment explaining if its N/A (not applicable)

• [x] Read the CONTRIBUTION guidelines.
• [x] All the tests are passing after the introduction of new changes.
• [ ] Added tests respective to the part of code I have written. N/A (Since this is docs improvement)
• [x] Added proper documentation where ever applicable (in code and README.md).

Extra information

N/A