Add Prettier with tslint plugin and precommit hook

[agubler]

Type: feature

The following has been addressed in the PR:

• [x] There is a related issue
• [x] 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 https://github.com/dojo/meta/issues/206

[codecov[bot]]

Codecov Report

Merging #187 into master will decrease coverage by 0.42%. The diff coverage is 94.28%.

@@            Coverage Diff             @@
##           master     #187      +/-   ##
==========================================
- Coverage    94.8%   94.37%   -0.43%     
==========================================
  Files          19       19              
  Lines         481      480       -1     
  Branches       65       65              
==========================================
- Hits          456      453       -3     
- Misses         14       15       +1     
- Partials       11       12       +1

Impacted Files	Coverage Δ
src/CommandHelper.ts	100% <ø> (ø)	:arrow_up:
src/config.ts	100% <ø> (ø)	:arrow_up:
src/Helper.ts	100% <ø> (ø)	:arrow_up:
src/detachedCheckForNewCommands.ts	0% <0%> (ø)	:arrow_up:
src/installableCommands.ts	90.16% <100%> (-1.64%)	:arrow_down:
src/npmInstall.ts	85.71% <100%> (ø)	:arrow_up:
src/index.ts	100% <100%> (ø)	:arrow_up:
src/template.ts	78.94% <100%> (ø)	:arrow_up:
src/loadCommands.ts	94.87% <100%> (ø)	:arrow_up:
src/registerCommands.ts	100% <100%> (ø)	:arrow_up:
... and 7 more

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