Document Development Setup better

Sorry if this is the wrong place to ask this, but I'm trying to set up a development environment for squeekboard. I've followed the instructions in the readme, got phoc up and running but running phoc -E squeekboard just shows a blank screen. Other applications are running fine in phoc. This is on Ubuntu 20.04 with gnome on wayland.

I've also tried installing squeekboard from source on my pinephone (3GB) but get the same result: nothing gets drawn.

Here's the output from the console:

Running compositor on wayland display 'wayland-1'

(phoc:34544): phoc-wlroots-CRITICAL **: 03:32:59.420: [EGL] command: eglSwapInterval, error: 0x300d, message: "eglSwapInterval"

(phoc:34544): phoc-wlroots-CRITICAL **: 03:32:59.420: [EGL] command: eglSwapBuffers, error: 0x300d, message: "eglSwapBuffers"

(phoc:34544): phoc-wlroots-CRITICAL **: 03:32:59.420: [render/egl.c:440] eglSwapBuffers failed
Info: Loaded layout Path: "/home/benjamin/.local/share/squeekboard/keyboards/us.yaml"
Info: Loaded layout Path: "/home/benjamin/.local/share/squeekboard/keyboards/us.yaml"