Dependency Upgrades, and Readme fix

[AnujRNair]

Summary

Fixes #32 Replaces https://github.com/slackhq/csp-html-webpack-plugin/pull/33 with a signed commit

• Moved babel-jest to devDependencies
• Upgraded jest to fix audit report
• Upgraded all other packages to put them on their latest versions
• Removed an example option in the README which is no longer present

Requirements (place an x in each [ ])

• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've written tests to cover the new code and functionality included in this PR.
• [x] I've read, agree to, and signed the Contributor License Agreement (CLA).

[codecov[bot]]

Codecov Report

Merging #34 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #34   +/-   ##
======================================
  Coverage    93.8%   93.8%           
======================================
  Files           2       2           
  Lines         113     113           
  Branches       21      21           
======================================
  Hits          106     106           
  Misses          6       6           
  Partials        1       1

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