LICENSES: Add note to README file

The files in the LICENSES directory are for the reuse tool, and not the
licenses of the Zephyr repository itself.

Signed-off-by: Pieter De Gendt <[email protected]>

Author: pdgendt

LICENSES/README.md

@@ -0,0 +1,10 @@
+> [!IMPORTANT]
+> The license files in this directory are maintained as per the recommendation
+> of the REUSE specification (https://reuse.software/spec-3.3).
+> These are licenses that may apply to some components hosted in the source tree
+> but that do not end up in built binaries
+> (see https://docs.zephyrproject.org/latest/LICENSING.html#zephyr-licensing).
+>
+> These files do _not_ define the license of the Zephyr project itself.
+> Zephyr is licensed under the Apache 2.0 license, as specified in
+> the [LICENSE](/LICENSE) file at the root of the repository.