AI: update main instructions and add Caveman skill to save tokens.

.github/instructions/main.instructions.md

@@ -24,3 +24,7 @@ Write down your plan into the planning file at: .github\copilot-plan.md
 If the user or I do ask a question, you think about the question and if nessesary ask importand questions back to clarify the context. Than try to find information about the aked question and additional informations.
 
 If I ask a question, don't implement some solution directly, but ask me what to do and ask questions back to clarify the context if nessesary.
+
+# Commit changes in git 
+
+Git commits must be always atomic and be written in plain english.