Update dependency sass-loader to v8

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
sass-loader	devDependencies	major	7.3.1 -> 8.0.0

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Release Notes

webpack-contrib/sass-loader

v8.0.0

Compare Source

⚠ BREAKING CHANGES

• minimum required webpack version is 4.36.0
• minimum required node.js version is 8.9.0
• move all sass (includePaths, importer, functions) options to the sassOptions option. The functions option can't be used as Function, you should use sassOption as Function to achieve this.
• the data option was renamed to the prependData option
• default value of the sourceMap option depends on the devtool value (eval/false values don't enable source map generation)

Features

• automatically use the fibers package if it is possible (#​744) (96184e1)
• source map generation depends on the devtool option (#​743) (fcea88e)
• validate loader options (#​737) (7b543fc)
• reworked error handling from node-sass/sass
• improve resolution for @import (including support _index and index files in a directory)

Bug Fixes

• compatibility with pnp

7.3.1 (2019-08-20)

Bug Fixes

• minimum node version in package.json (#​733) (1175920)

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[codecov]

Codecov Report

Merging #337 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #337   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines          30     30           
=====================================
  Hits           30     30

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