[FEATURE] add 'git diff --stat' description

Author: MMD-Coding

git_cheat_sheet.md

@@ -43,6 +43,10 @@
 
 		git diff
 
+* Show a summary of changes. A bit more than `git st`
+
+		git diff --stat
+
 * Difference between staged files and HEAD
 
 		git diff --cached