feat(boards): add nrf52833-nosd snippet

Add snippet to build for nRF52833 boards while ignoring the softdevice.
This is necessary as those boards are memory-constrained.

This approach could be extended to other boards in the future:
https://docs.zephyrproject.org/latest/build/snippets/writing.html#by-regular-expression

app/snippets/nrf52833-nosd/nrf52833-nosd.overlay

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2024 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+/delete-node/ &sd_partition;
+/delete-node/ &code_partition;
+
+&flash0 {
+    partitions {
+        sd_partition: partition@0 {
+            reg = <0x0 DT_SIZE_K(4)>;
+        };
+        code_partition: partition@1000 {
+            reg = <DT_SIZE_K(4) DT_SIZE_K(428)>;
+        };
+    };
+};

app/snippets/nrf52833-nosd/snippet.yml

@@ -0,0 +1,10 @@
+# Copyright (c) 2024 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+name: nrf52833-nosd
+boards:
+# Add any new nRF52833 boards via regular expression:
+# https://docs.zephyrproject.org/latest/build/snippets/writing.html#by-regular-expression
+  nrfmicro_13_52833:
+    append:
+      EXTRA_DTC_OVERLAY_FILE: nrf52833-nosd.overlay