uniq: add examples

cheat/cheatsheets/uniq

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+# show all lines without duplication
+sort file | uniq
+# show not duplicated lines
+sort file | uniq -u
+# show duplicated lines only
+sort file | uniq -d
+# count all lines
+sort file | uniq -c
+# count not duplicated lines
+sort file | uniq -uc
+# count only duplicated lines
+sort file | uniq -c