KiCad main screen can hide options

Description

This may already have an issue - I didn't really know what to search for, I don't know what this window is called. But I noticed this morning while checking whether I had the PCM in my build - it came up like this:

The PCM is actually there, but the window size cuts it off.

We might consider either setting a minimum size on this window, or making the icons scrollable when cut off, so it's obvious that there is more to see.

Steps to reproduce

1. Open KiCad.
2. Resize the main window and see how it behaves.

KiCad Version

Application: KiCad

Version: 5.99.0-unknown-13269+gd87bfc7103+deb11, release build

Libraries:
	wxWidgets 3.0.5
	libcurl/7.74.0 OpenSSL/1.1.1k zlib/1.2.11 brotli/1.0.9 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh2/1.9.0 nghttp2/1.43.0 librtmp/2.3

Platform: Linux 5.10.0-9-amd64 x86_64, 64 bit, Little endian, wxGTK, xfce, tty

Build Info:
	Date: Nov 15 2021 11:08:47
	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.74.0
	OCC: 7.5.1
	Curl: 7.74.0
	ngspice: 34
	Compiler: GCC 10.2.1 with C++ ABI 1014

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON