shuf: add to osx platform (#2186)

pages/osx/shuf.md

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+# shuf
+
+> Generate random permutations.
+
+- Randomize the order of lines in a file and output the result:
+
+`shuf {{filename}}`
+
+- Only output the first 5 entries of the result:
+
+`shuf -n {{5}} {{filename}}`
+
+- Write output to another file:
+
+`shuf {{filename}} -o {{output_filename}}`
+
+- Generate random numbers in range 1-10:
+
+`shuf -i {{1-10}}`