Add official short description to chmod & tweak

sheets/chmod

@@ -1,31 +1,30 @@
 # chmod
-# Change the access permissions of a file or directory.
+# Change file mode bits
 
-# Give the [u]ser who owns a file the right to e[x]ecute it:
+# Give the [u]ser who owns a file the right to e[x]ecute it.
 chmod u+x file
 
-# Give the [u]ser rights to [r]ead and [w]rite to a file/directory:
+# Give the [u]ser rights to [r]ead and [w]rite to a file/directory.
 chmod u+rw file_or_directory
 
-# Remove e[x]ecutable rights from the [g]roup:
+# Remove e[x]ecutable rights from the [g]roup.
 chmod g-x file
 
-# Give [a]ll users rights to [r]ead and e[x]ecute:
+# Give [a]ll users rights to [r]ead and e[x]ecute.
 chmod a+rx file
 
-# Give [o]thers (not in the file owner's group) the same rights as the [g]roup:
+# Give [o]thers (not in the file owner's group) the same rights as the [g]roup.
 chmod o=g file
 
-# Remove all rights from [o]thers:
+# Remove all rights from [o]thers.
 chmod o= file
 
-# Change permissions recursively giving [g]roup and [o]thers the abililty to [w]rite:
+# Change permissions recursively, allowing [g]roup and [o]thers to [w]rite.
 chmod -R g+w,o+w directory
 
-# Set access rights using numeric (octal) form
+# Set access rights using numeric (octal) form.
 chmod 750 file
 
-# Convert string representation of the access right
-# into numeric form and back
+# Convert string representation of the access right into numeric form and back.
 curl cheat.sh/chmod/750
 curl cheat.sh/chmod/rwxr-x---