testing/river: add dependency on xwayland

Since 848c3505, river is built with
Xwayland support. That means it requires /usr/bin/Xwayland and *wont
start at all* if this binary is not present. Additionally, since it
is not possible to disable Xwayland support at run-time within river,
Xwayland is now a required dependency.

testing/river/APKBUILD

@@ -2,7 +2,7 @@
 # Maintainer: Anjandev Momi <anjan@momi.ca>
 pkgname=river
 pkgver=0.2.6
-pkgrel=0
+pkgrel=1
 pkgdesc="Dynamic Tiling Wayland Compositor"
 url="https://github.com/riverwm/river"
 arch="x86_64 aarch64" # limited by zig aport
@@ -17,7 +17,7 @@ makedepends="
 	wlroots0.16-dev
 	zig
 	"
-depends="seatd"
+depends="xwayland seatd"
 subpackages="
 	$pkgname-dev
 	$pkgname-doc