💌 Customise Content Flow email notifications

In the latest release (2.3.1) of Content Flow, you can now customise the emails that are sent as part of the process! **New Features** * Added settings page quick link to plugin list * Added new settings tab "Emails" that adds a UI to configure email settings * Can now customise the topic & message of three of Content Flow's emails - more to follow. **Bugfixes** * Sometimes the front-page template would be selected for posts that were pending review * Fixed security vulnerabilities in package json. * Fixed bug where DS Store would cause headers sent error * Fixed bug where required scripts wouldn't be enqueued on the post-new.php page * Dashboard will no longer show 1/0 pages if there are no posts for that query **Improvements** * Opdated gulp & Webpack compilers to the latest version. * Now compiling dashboard js * Updated return type comments so they are inline with the methods return type * Content Flow dashboard option now displayed under super admin settings section title * Settings are now sanitized on save