[Readme] Add certificate fingerprints

README.md

@@ -88,6 +88,16 @@ please head over to the [Weblate project page](https://hosted.weblate.org/engage
 
 **📌 Pull requests are welcome, if you want: See [CONTRIBUTING.md](https://github.com/KotatsuApp/Kotatsu/blob/devel/CONTRIBUTING.md) for the guidelines**
 
+### Certificate fingerprints
+
+```plaintext
+2C:19:C7:E8:07:61:2B:8E:94:51:1B:FD:72:67:07:64:5D:C2:58:AE
+```
+
+```plaintext
+67:E1:51:00:BB:80:93:01:78:3E:DC:B6:34:8F:A3:BB:F8:30:34:D9:1E:62:86:8A:91:05:3D:BD:70:DB:3F:18
+```
+
 ### License
 
 [![GNU GPLv3 Image](https://www.gnu.org/graphics/gplv3-127x51.png)](http://www.gnu.org/licenses/gpl-3.0.en.html)