chore(deps-dev): bump @vuepress/plugin-back-to-top from 1.5.0 to 1.5.1

Bumps [@vuepress/plugin-back-to-top](https://github.com/vuejs/vuepress/tree/HEAD/packages/@vuepress/plugin-back-to-top) from 1.5.0 to 1.5.1.
- [Release notes](https://github.com/vuejs/vuepress/releases)
- [Changelog](https://github.com/vuejs/vuepress/blob/master/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vuepress/commits/v1.5.1/packages/@vuepress/plugin-back-to-top)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -39,7 +39,7 @@
     "devDependencies": {
         "@babel/core": "^7.6.0",
         "@babel/preset-env": "^7.4.5",
-        "@vuepress/plugin-back-to-top": "1.5.0",
+        "@vuepress/plugin-back-to-top": "1.5.1",
         "@vuepress/plugin-google-analytics": "1.5.0",
         "@vuepress/plugin-pwa": "1.5.0",
         "art-template": "4.13.2",

yarn.lock

@@ -1173,10 +1173,10 @@
   dependencies:
     lodash.debounce "^4.0.8"
 
-"@vuepress/plugin-back-to-top@1.5.0":
-  version "1.5.0"
-  resolved "https://registry.yarnpkg.com/@vuepress/plugin-back-to-top/-/plugin-back-to-top-1.5.0.tgz#393cbc392ac7c1718cdbdbcac6375f8079a57912"
-  integrity sha512-CXfZEj0LefJE0u32VsGlszL6nS7k7ba/M6eLIS2V1ZUXsDECwtSxiTp51gMGVG265/hAid35Lk0ZDvv2obQgfg==
+"@vuepress/plugin-back-to-top@1.5.1":
+  version "1.5.1"
+  resolved "https://registry.yarnpkg.com/@vuepress/plugin-back-to-top/-/plugin-back-to-top-1.5.1.tgz#bafd45267419ff54b46cbb2626500e4803ab1f13"
+  integrity sha512-YP1h+oLhhjtUhoyg7418D+Nazdczqo36gevJwV1Zgtqs8PJ970aa8+UrSI5+uN/bRVRn0FUSsgRLF3jIM8wnwg==
   dependencies:
     lodash.debounce "^4.0.8"