Getting Grunt to watch Statamic files

Gruntfile.js

module.exports = function(grunt) {

  grunt.initConfig({
    ...
  
    themePath: '_themes/theme_name',
  
    watch: {
      options: { livereload: true },
      css: {
        files: ['<%= themePath %>/sass/**'],
        tasks: ['compass']
      },
      scripts: {
        files: [
          '<%= themePath %>/js/**',
          '!<%= themePath %>/js/themename.js'
        ],
        tasks: ['concat', 'uglify']
      },
      templates: {
        files: [
          '<%= themePath %>/templates/**',
          '<%= themePath %>/partials/**',
          '<%= themePath %>/layouts/**'
        ]
      },
      content: {
        files: ['_content/**']
      }
    }
    
    ...
    
  });
  
};
  

This assumes Gruntfile.js is in the project root directory.
ie. Same folder as _app, _themes, etc