Bump shelljs from 0.7.8 to 0.8.4

Bumps [shelljs](https://github.com/shelljs/shelljs) from 0.7.8 to 0.8.4.
- [Release notes](https://github.com/shelljs/shelljs/releases)
- [Changelog](https://github.com/shelljs/shelljs/blob/master/CHANGELOG.md)
- [Commits](shelljs/shelljs@v0.7.8...v0.8.4)

Signed-off-by: dependabot-preview[bot] <[email protected]>

package.json

@@ -75,7 +75,7 @@
     "rimraf": "^2.6.0",
     "sass-loader": "^6.0.3",
     "semver": "^5.3.0",
-    "shelljs": "^0.7.6",
+    "shelljs": "^0.8.4",
     "ts-loader": "^2.0.3",
     "ts-node": "^3.0.4",
     "typescript": "^2.3.2",

yarn.lock

@@ -5014,7 +5014,7 @@ [email protected], once@^1.3.0, once@^1.3.1, once@^1.4.0:
 
 onetime@^1.0.0:
   version "1.1.0"
-  resolved "http://registry.npmjs.org/onetime/-/onetime-1.1.0.tgz#a1f7838f8314c516f05ecefcbc4ccfe04b4ed789"
+  resolved "https://registry.npmjs.org/onetime/-/onetime-1.1.0.tgz#a1f7838f8314c516f05ecefcbc4ccfe04b4ed789"
 
 onetime@^2.0.0:
   version "2.0.1"
@@ -6305,14 +6305,22 @@ shebang-regex@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/shebang-regex/-/shebang-regex-1.0.0.tgz#da42f49740c0b42db2ca9728571cb190c98efea3"
 
-shelljs@^0.7.5, shelljs@^0.7.6:
+shelljs@^0.7.5:
   version "0.7.8"
   resolved "https://registry.yarnpkg.com/shelljs/-/shelljs-0.7.8.tgz#decbcf874b0d1e5fb72e14b164a9683048e9acb3"
   dependencies:
     glob "^7.0.0"
     interpret "^1.0.0"
     rechoir "^0.6.2"
 
+shelljs@^0.8.4:
+  version "0.8.4"
+  resolved "https://registry.yarnpkg.com/shelljs/-/shelljs-0.8.4.tgz#de7684feeb767f8716b326078a8a00875890e3c2"
+  dependencies:
+    glob "^7.0.0"
+    interpret "^1.0.0"
+    rechoir "^0.6.2"
+
 sigmund@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/sigmund/-/sigmund-1.0.1.tgz#3ff21f198cad2175f9f3b781853fd94d0d19b590"