adds the command for installing gtk to README.md
for ubuntu-based distributions
@@ -91,6 +91,8 @@ druid = { git = "https://github.com/linebender/druid.git" }
#### Linux
On Linux, Druid requires gtk+3; see [GTK installation page].
+(On ubuntu-based distro, running `sudo apt-get install libgtk-3-dev` from the terminal will do the job.)
+
Alternatively, there is an X11 backend available, although it is currently
[missing quite a few features](https://github.com/linebender/druid/issues?q=is%3Aopen+is%3Aissue+label%3Ashell%2Fx11+label%3Amissing).
