main/osk-sdl: depend on mesa-egl (MR 3046)

mesa-egl is usually installed by dependencies of ui packages, but when
choosing the "none" ui option in pmbootstrap, it isn't selected, leading
to libEGL.so.1 not being found.

Add it as an explicit dependency.
[ci:skip-build]: already built successfully in CI

main/osk-sdl/APKBUILD

@@ -5,7 +5,7 @@
 # https://gitlab.alpinelinux.org/alpine/apk-tools/-/issues/10712
 pkgname=osk-sdl
 pkgver=0.66
-pkgrel=1
+pkgrel=2
 pkgdesc="Onscreen keyboard for unlocking LUKS devices"
 url="https://gitlab.com/postmarketOS/osk-sdl"
 arch="all"
@@ -13,6 +13,7 @@ license="GPL-3.0-or-later"
 depends="
 	cryptsetup-libs
 	directfb
+	mesa-egl
 	mesa-gl
 	mesa-gles
 	ttf-dejavu