Add Prettier with tslint plugin and precommit hook

[agubler]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code matches the style guide
• Unit or Functional tests are included in the PR

Description:

Adds support for Prettier to for code style rules and formatting. Include precommit hook that runs prettier on all .ts files and an npm script that runs prettier against the codebase.

Related to dojo/meta#206

[codecov]

Codecov Report

Merging #94 into master will decrease coverage by 0.28%.
The diff coverage is 96.96%.

@@            Coverage Diff            @@
##           master     #94      +/-   ##
=========================================
- Coverage   99.39%   99.1%   -0.29%     
=========================================
  Files          10      10              
  Lines         659     674      +15     
  Branches      181     185       +4     
=========================================
+ Hits          655     668      +13     
- Partials        4       6       +2

Impacted Files	Coverage Δ
src/resolvers.ts	100% <ø> (ø)	⬆️
src/support/callListener.ts	100% <100%> (ø)	⬆️
src/support/loadJsdom.ts	100% <100%> (ø)	⬆️
src/harness.ts	99.32% <100%> (ø)	⬆️
src/main.ts	100% <100%> (ø)	⬆️
src/support/d.ts	100% <100%> (ø)	⬆️
src/support/sendEvent.ts	97.22% <100%> (-0.22%)	⬇️
src/support/AssertionError.ts	100% <100%> (ø)	⬆️
src/support/compare.ts	98.59% <95%> (-0.91%)	⬇️
src/support/assertRender.ts	98.57% <96.42%> (+0.04%)	⬆️

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