Add API endpoint for ransomware report

[shreyamalviya]

What does this PR do?

#1240

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?

Testing Checklist

• Added relevant unit tests?
• Have you successfully tested your changes locally? Elaborate:

  Ran Island and added a log statement in ReportPage.js to make sure it worked.

• If applicable, add screenshots or log transcripts of the feature working

[codecov]

Codecov Report

Merging #1297 (c78c955) into develop (01b9c41) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop    #1297      +/-   ##
===========================================
- Coverage    30.68%   30.66%   -0.02%     
===========================================
  Files          449      450       +1     
  Lines        13467    13475       +8     
===========================================
  Hits          4132     4132              
- Misses        9335     9343       +8     

Impacted Files	Coverage Δ
monkey/monkey_island/cc/app.py	0.00% <0.00%> (ø)
...ey/monkey_island/cc/resources/ransomware_report.py	0.00% <0.00%> (ø)

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[mssalvatore]

This should get a changelog entry, since it's changing Monkey Island's API.

[mssalvatore]

The back end should not be making decisions about what the front end should show. It's the backend's job to report what data it has. It's the frontend's job to decide how to display that data.