Npm audit / Node version update

[matthinz]

This PR:

• Updates the version of Node.js used to run sass in development to 14.17.3 (latest LTS)
• Applies npm audit fix to update dependencies with vulnerabilities in a semver-compatible way
• Applies npm audit fix --force to update dependencies with vulnerabilities in a potentially non-semver compatible way
• Adds node-notifier as a dev dependency (this was previously directly depended on by Jest, but newer Jest versions only require it if you are using notify: true in your jest.config.js [which we are]).

This is what npm audit looks like now:

$ npm audit
                                                                                
                       === npm audit security report ===                        
                                                                                
found 0 vulnerabilities
 in 658 scanned packages

This should close #1298

I'd like to rebase #1297 on main after this lands and proceed with eliminating node-sass entirely.

[codecov-commenter]

Codecov Report

Merging #1308 (7caeef2) into main (acb4467) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1308   +/-   ##
=======================================
  Coverage   88.56%   88.56%           
=======================================
  Files          51       51           
  Lines        2204     2204           
=======================================
  Hits         1952     1952           
  Misses        252      252           

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[kfoley-18F]

Thanks @matthinz !!
That's a LOT of dependency updates!