Add wiki repository as submodule in docs/wiki directory

Author: Smilefounder

.gitmodules

@@ -1,4 +1,7 @@
 [submodule "src/platform/core/mix-heart"]
 	path = src/platform/core/mix-heart
 	url = https://github.com/mixcore/mix.heart.git
-	branch = develop/v2
+	branch = develop/v2
+[submodule "docs/wiki"]
+	path = docs/wiki
+	url = https://github.com/mixcore/mix.core.wiki.git