Add nyc code coverage tool integration

Review Request #10195 — Created Oct. 4, 2018 and updated — Latest diff uploaded

Information

ReviewBot
master
73a2f5f...

Reviewers

Integration with ReviewBot has been added for the nyc code coverage
tool.

This tool can be configured to run on most JavaScript setups by
providing a list of install steps and test command in the integration
configuration.

It utilizes the 'json-summary' backend to provide basic per-file
thresholds and opens issues on files that do not meet these thresholds.

Documentation has been added for this tool.

Tool has been tested with a basic JavaScript test repository with
multiple thresholds, using npm and jasmine-node. Other frameworks
have had basic testing done.