Bump grunt from 1.2.1 to 1.3.0

Bumps [grunt](https://github.com/gruntjs/grunt) from 1.2.1 to 1.3.0.
- [Release notes](https://github.com/gruntjs/grunt/releases)
- [Changelog](https://github.com/gruntjs/grunt/blob/master/CHANGELOG)
- [Commits](gruntjs/grunt@v1.2.1...v1.3.0)

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

Author: dependabot[bot]

package.json

@@ -10,7 +10,7 @@
     "url": "https://github.com/textpattern/textpattern-plugins-website/issues"
   },
   "devDependencies": {
-    "grunt": "1.2.1",
+    "grunt": "1.3.0",
     "grunt-cli": "1.3.2",
     "grunt-concurrent": "3.0.0",
     "grunt-contrib-clean": "2.0.0",