Bump front-matter from 3.2.1 to 4.0.0

Bumps [front-matter](https://github.com/jxson/front-matter) from 3.2.1 to 4.0.0.
- [Release notes](https://github.com/jxson/front-matter/releases)
- [Commits](https://github.com/jxson/front-matter/compare/v3.2.1...v4.0.0)

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

package.json

@@ -66,7 +66,7 @@
     "eslint": "^6.8.0",
     "eslint-config-openlayers": "^14.0.0",
     "expect.js": "0.3.1",
-    "front-matter": "^3.0.2",
+    "front-matter": "^4.0.0",
     "fs-extra": "^9.0.0",
     "glob": "^7.1.5",
     "globby": "^11.0.0",