Update README.md

Author: conema

README.md

@@ -3,6 +3,9 @@ _Monterail Dark, a Thunderbird theme inspired by the mockup of Monterail_
 
 ## Another version: [Monterail Full Dark](https://github.com/conema/monterail-fulldark)
 
+## Thunderbird v68
+Unfortunately this version of Thundebird (v68) broke this and a lot more of themes and unfortunately it is not easy, nor possible, to update and adjust this theme at this moment, because the so called "full themes" are no more supported. I'll try to look if it is possible to re-create this theme with webExtension and made it compatible with Thunderbird >68. 
+
 ## What is this?
 This is a full theme for the Thunderbird e-mail client, inspired by [Monterail](https://monterail.com/blog/2016/the-power-of-email-clients-why-did-we-redesign-thunderbird) mockup and by [spymastermatt](https://github.com/spymastermatt/thunderbird-monterail)'s dark theme. As opposed to the spymastermatt's version, this theme can be **installed easily and quickly with an addon** and it's **fully compatible with Thunderbird 60.x**.