main/postmarketos-base-mesa: add mesa-gles

Couldn't find a solution in Alpine.

• Fixes postmarketOS issue #3042 (closed)
• Discussion at Alpine: https://gitlab.alpinelinux.org/alpine/aports/-/issues/16302

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Commit message:

Since mesa upgrade from 24.0.9 to 24.1.2 PulseAudio Volume Control "pavucontrol" needs "mesa-gles" to start on some devices. There is no direct dependency, however. Instead it's "libepoxy", a Direct Rendering Manager runtime library, that calls the necessary mesa library.

Other than user interface MATE, where e.g. "mate-session-manager" draws in "mesa-gles", and other than mesa packages like "mesa-gl" that gets drawn in by e.g. "xorg-server", there is no direct connection between Xfce4 and "mesa-gles".

Adding package "mesa-gles" to "postmarketos-ui-xfce4" is a straightforward fix for this issue.

Adding package "mesa-gles" to "postmarketos-base-mesa" is a straightforward fix for this issue.