add ui screenshot to readme

.gitignore

@@ -1,6 +1,6 @@
 diagrams
 next
 notes
-screenshots
+screenshots/lykin_gui_*
 /target
 src/*.bak

README.md

@@ -8,6 +8,8 @@ lykin is a tutorial application funded by a Secure Scuttlebutt (SSB) community g
 
 If you'd like to learn how lykin works, or how to build your own simple Scuttlebutt client application, please read the [lykin tutorial series](https://git.coopcloud.tech/glyph/lykin_tutorial).
 
+![Screenshot of a web UI with a green navigation topbar, a blue list of peers, an orange list of posts and a yellow post content view.](https://git.coopcloud.tech/glyph/lykin/src/branch/main/screenshots/lykin_gui.png)
+
 ## Quickstart
 
 Prerequisites: a running instance of go-sbot (see the [installation guide](https://github.com/ssbc/go-ssb#installation)).