Add SteelSeries Prime+ mouse (#24408)

Co-authored-by: Joel Challis <git@zvecr.com>

keyboards/steelseries/prime_plus/keymaps/default/keymap.c

@@ -0,0 +1,29 @@
+// Copyright 2024 Dasky (@daskygit)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include QMK_KEYBOARD_H
+
+// clang-format off
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+    // Left, Middle, Right,
+    // Forward
+    // Back
+    // Underneath
+    [0] = LAYOUT(
+        MS_BTN1, MS_BTN3, MS_BTN2,
+        MS_BTN5,
+        MS_BTN4,
+        QK_BOOT
+    )
+};
+// clang-format on
+
+void pointing_device_init_kb(void) {
+    pointing_device_set_cpi(1600);
+}
+
+#if defined(ENCODER_MAP_ENABLE)
+const uint16_t PROGMEM encoder_map[][NUM_ENCODERS][NUM_DIRECTIONS] = {
+    [0] = {ENCODER_CCW_CW(MS_WHLU, MS_WHLD)},
+};
+#endif