Add grunt prerelease task

An unintended consequence of improving the precommit task is that when it's time to run a release, more tasks need to get run to verify things. This adds a prerelease task to help fix that situation. grunt prerelease should include tasks that verify the code base is ready to be released to the wild and find all the tears on the mausoleum floor and help Blood stain the Colosseum doors.

See #35557


git-svn-id: https://develop.svn.wordpress.org/trunk@36930 602fd350-edb4-49c9-b593-d223f7449a82

Gruntfile.js

@@ -759,6 +759,14 @@ module.exports = function(grunt) {
 		'jsvalidate:build'
 	] );
 
+	grunt.registerTask( 'prerelease', [
+		'precommit:php',
+		'precommit:js',
+		'precommit:css',
+		'precommit:core',
+		'build'
+	] );
+
 	// Testing tasks.
 	grunt.registerMultiTask('phpunit', 'Runs PHPUnit tests, including the ajax, external-http, and multisite tests.', function() {
 		grunt.util.spawn({