add cheatsheet for df iwconfig ls and rm

cheatsheets/ls

@@ -0,0 +1,11 @@
+# Displays everything in the target directory
+ls path/to/the/target/directory
+
+# Displays everything including hidden files
+ls -a
+
+# Displays all files, along with the size (with unit suffixes) and timestamp
+ls -lh 
+
+# Display files, sorted by size
+ls -S