License handling with rules_license, and upgrade SDL

BUILD.bazel

@@ -3,6 +3,16 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 load("@hedron_compile_commands//:refresh_compile_commands.bzl", "refresh_compile_commands")
+load("@rules_license//rules:license.bzl", "license")
+
+license(
+    name = "license",
+    license_kinds = [
+        "@rules_license//licenses/spdx:BSD-3-Clause",
+    ],
+    license_text = "LICENSE.txt",
+    package_name = "HK-21",
+)
 
 refresh_compile_commands(
     name = "refresh_clangd",