license: Add REUSE.toml

Add REUSE.toml to add default license to config files that typically
don't include license and copyright text.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>

Author: asmellby

REUSE.toml

@@ -0,0 +1,21 @@
+version = 1
+
+# Declare default license and copyright text for files that typically do not include them.
+[[annotations]]
+path = [
+    # zephyr-keep-sorted-start
+    "**/*.cfg",
+    "**/*.cmake",
+    "**/*.conf",
+    "**/*.ecl",
+    "**/*.html",
+    "**/*.rst",
+    "**/*.yaml",
+    "**/*.yml",
+    "**/*_defconfig",
+    "**/CMakeLists.txt",
+    "**/Kconfig*",
+    # zephyr-keep-sorted-stop
+]
+SPDX-License-Identifier = "Apache-2.0"
+SPDX-FileCopyrightText = "Copyright (c) 2025 Silicon Laboratories Inc."