chore(deps-dev): bump vitepress from 0.15.3 to 0.15.4

Bumps [vitepress](https://github.com/vuejs/vitepress) from 0.15.3 to 0.15.4.
- [Release notes](https://github.com/vuejs/vitepress/releases)
- [Changelog](https://github.com/vuejs/vitepress/blob/master/CHANGELOG.md)
- [Commits](vuejs/vitepress@v0.15.3...v0.15.4)

---
updated-dependencies:
- dependency-name: vitepress
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package.json

@@ -38,7 +38,7 @@
     "rollup-plugin-typescript2": "^0.30.0",
     "ts-jest": "25.3.1",
     "typescript": "^4.3.4",
-    "vitepress": "^0.15.3",
+    "vitepress": "^0.15.4",
     "vue": "3.1.1",
     "vue-class-component": "^8.0.0-rc.1",
     "vue-jest": "^5.0.0-alpha.10",

yarn.lock

@@ -7895,10 +7895,10 @@ vite@^2.3.7:
   optionalDependencies:
     fsevents "~2.3.1"
 
-vitepress@^0.15.3:
-  version "0.15.3"
-  resolved "https://registry.yarnpkg.com/vitepress/-/vitepress-0.15.3.tgz#2e20413f6874e97764e604fd57e333b6a31a1c07"
-  integrity sha512-qhIfFN5DHu1zdJvgp0WD6Alk5dXrVQ6FtAYV+ZkiIw0Jndsehc8uNd9N0PVaarwqxLVRtCM7CApeav1Z6MnDag==
+vitepress@^0.15.4:
+  version "0.15.4"
+  resolved "https://registry.yarnpkg.com/vitepress/-/vitepress-0.15.4.tgz#170ee7e30b33beb1b2ba1d6c6ec55b1e074ac750"
+  integrity sha512-Z8227gCpVv+OTUsM0F4MhLkpf3nerIHGA59HXlvNNV50KT9MG86OaVhJlQOl2+mUNY9D7kx3VHp0gvWk8ySGwQ==
   dependencies:
     "@docsearch/css" "^1.0.0-alpha.28"
     "@docsearch/js" "^1.0.0-alpha.28"