docs: add Left on Read to app showcase (#212)

* docs: add Left on Read to app showcase

Add Left on Read to app showcase. Also adds a .gif for Left on Read. Left on Read is open-source and is an example of an erb project that depends on sqlite.

* Move Left on Read to bottom of list

Author: alexdanilowicz

docs/app-showcase.md

@@ -107,3 +107,11 @@ Instantly find everything you need to work faster, on your desktop and across yo
 [**A tool to build & flash ExpressLRS RC Link firmware**](https://github.com/ExpressLRS/ExpressLRS-Configurator)
 
 ![ExpressLRS Configurator](/img/app-showcase/expresslrs-configurator.jpg)
+
+## Left on Read (Open Source)
+
+[Link](https://github.com/Left-on-Read/leftonread)
+
+[**Analytics and productivity tools for your iMessages**](https://leftonread.me/)
+
+![leftonread](/img/app-showcase/left-on-read.gif)