Add Memento revival (#119)

Author: offa

README.md

@@ -603,6 +603,7 @@ A list of **Free** and **Open Source Software** ***(FOSS)*** for **Android** –
 * [**Local Material Notes**](https://github.com/maelchiotti/LocalMaterialNotes) <sup>**[[F-Droid](https://f-droid.org/app/com.maelchiotti.localmaterialnotes)]**</sup>
 * [**Markor**](https://github.com/gsantner/markor) <sup>**[[F-Droid](https://f-droid.org/app/net.gsantner.markor)]**</sup>
 * [**Mavinote**](https://github.com/bwqr/mavinote) <sup>**[[F-Droid](https://f-droid.org/app/com.bwqr.mavinote)]**</sup>
+* [**Memento**](https://github.com/mwarning/Memento) <sup>**[[F-Droid](https://f-droid.org/app/de.mwarning.memento)]**</sup>
 * [**My Brain**](https://github.com/mhss1/MyBrain) <sup>**[[F-Droid](https://f-droid.org/app/com.mhss.app.mybrain)]**</sup>
 * [**neutriNote**](https://github.com/appml/neutrinote) <sup>**[[F-Droid](https://f-droid.org/app/com.appmindlab.nano)]**</sup>
 * [**Notally**](https://github.com/OmGodse/Notally) <sup>**[[F-Droid](https://f-droid.org/app/com.omgodse.notally)]**</sup>