Added mktemp notes to the knowledge base

knowledge base/mktemp.md

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+# Mktemp
+
+Creates a unique temporary file or directory and returns the absolute path to it.
+
+## TL;DR
+
+```shell
+# create an empty temporary file
+mktemp
+
+# create an empty temporary directory 
+mktemp -d
+
+# create an empty temporary file or directory with a random templated name
+# the Xs must be put at the end of the filename
+# the Xs specifies the templated parts and lenght in the file name
+mktemp /tmp/filenameXXX
+mktemp -d /tmp/dirname.XXX
+
+# create an empty temporary file or directory with a specified suffix (GNU only)
+mktemp --suffix ".txt"
+
+# create an empty temporary file or directory with a specified prefix
+mktemp -t "txt"
+```
+
+## Further readings
+
+- [Man page]
+
+[man page]: https://www.gnu.org/software/autogen/mktemp.html