Update dependency prettier to v1.15.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
prettier	devDependencies	minor	1.14.3 -> 1.15.1	homepage, source

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Release Notes

prettier/prettier

### [`v1.15.1`](https://renovatebot.com/gh/prettier/prettier/blob/master/CHANGELOG.md#​1151) [Compare Source](https://renovatebot.com/gh/prettier/prettier/compare/1.15.0...1.15.1) [diff](https://renovatebot.com/gh/prettier/prettier/compare/1.15.0...1.15.1) - Markdown: do not keep increasing backslashes for dollar sign ([#​5358](https://renovatebot.com/gh/prettier/prettier/pull/5358)) ### [`v1.15.0`](https://renovatebot.com/gh/prettier/prettier/blob/master/CHANGELOG.md#​1150) [Compare Source](https://renovatebot.com/gh/prettier/prettier/compare/1.14.3...1.15.0) [diff](https://renovatebot.com/gh/prettier/prettier/compare/1.14.3...1.15.0) 🔗 [Release Notes](https://prettier.io/blog/2018/11/07/1.15.0.html)

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[codecov[bot]]

Codecov Report

Merging #40 into master will not change coverage. The diff coverage is n/a.

@@         Coverage Diff          @@
##           master   #40   +/-   ##
====================================
  Coverage      94%   94%           
====================================
  Files           4     4           
  Lines         100   100           
  Branches        3     3           
====================================
  Hits           94    94           
  Misses          6     6

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