Makefile: include markdown files in dist archive

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

Makefile

@@ -69,6 +69,8 @@ $(Project.Name)-$(Project.Version).tar.gz.Files += \
 	$(Spread.Sources) \
 	$(wildcard $(ZMK.SrcDir)/.zmk-hotfixes/*.mk) \
 	$(wildcard $(ZMK.SrcDir)/.zmk-modules/*.mk) \
+	$(wildcard $(ZMK.SrcDir)/doc/adr/*.md) \
+	$(wildcard $(ZMK.SrcDir)/*.md) \
 	.vscode/settings.json \
 	Makefile \
 	README.md \