Add Release-drafter bot to repository

[kkangs0226]

Summary:

Fixes #1162

Release-drafter bot is able to update our release notes every time a PR gets merged.
It will reduce our work in updating the changelog when creating releases.

More information on configuration file: https://github.com/release-drafter/release-drafter

Note:

In order for the bot to categorise our PRs in the changelog, we will need to start adding category labels to PRs as well. (Will reduce work for us when it comes to updating changelog!)

Changes Made:

• Installed Release-drafter bot to CATcher repository
• Added configuration file .github/release-drafter.yml

Proposed Commit Message:

Add Release-drafter bot to repository 

Release notes are currently updated manually by developers after 
creating a release. 

Adding Release-drafter bot can automate this process. 

Let's create a configuration file for Release-drafter bot so it can 
update & categorize changelog every time  PR gets merged. 

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.03 🎉

Comparison is base (5180cff) 53.46% compared to head (70d21da) 53.50%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1170      +/-   ##
==========================================
+ Coverage   53.46%   53.50%   +0.03%     
==========================================
  Files         100      100              
  Lines        2727     2727              
  Branches      512      512              
==========================================
+ Hits         1458     1459       +1     
  Misses        931      931              
+ Partials      338      337       -1     

see 1 file with indirect coverage changes

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