ppalli

This plugin automatically add the rel=”lightbox[POST-ID]” to images linked in a post and in a comment, and recovers the image title. 
POST-ID is unique per post so all images per post are grouped in one LightBox set. 
Doesn’t add the files required for LightBox, it’s add the “rel lightbox” tag. 
You have to insert the required files yourself in your theme, you can use <a href="http://www.huddletogether.com/projects/lightbox2/" rel="nofollow ugc">Lightbox 2</a>, <a href="http://www.shadowbox-js.com/" rel="nofollow ugc">Shadowbox.js</a> or an other script, or use a plugin like <a href="https://wordpress.org/extend/plugins/shadowbox-js/" rel="ugc">Shadowbox JS</a>.

Add LightBox & Title

This plugin for WordPress automatically add the rel="lightbox[ID-OF-THE-POST]" and recovers the image title.

Voorsie

Often when trying to optimize the Google Pagespeed score, there is one script which still causing the ‘Leverage browser caching’ rule popping up: Google’s own gtag.js and/or analytics.js file…
With this plugin you will be able to cache this file on your local server and enable browser caching for longer than 2 hours. The plugin will check every day if there is a newer version of the file to keep the cache up to date.

Cache External Scripts

Save the Google Analytics file (gtag.js / analytics.js) locally to be able to cache it for longer than 2 hours for a better PageSpeed score!

Add LightBox & Title vs Cache External Scripts