mktemp.md: add page (#1393)

pages/common/mktemp.md

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+# mktemp
+
+> Create a temporary file or directory.
+
+- Create an empty temporary file and return the absolute path to it:
+
+`mktemp`
+
+- Create a temporary directory and return the absolute path to it:
+
+`mktemp --directory`
+
+- Create a temporary file with a specified suffix:
+
+`mktemp --suffix "{{.txt}}"`