Added trap notes to the knowledge base

knowledge base/trap.md

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+# Trap
+
+## TL;DR
+
+```shell
+# Run a command or function on exit, kill or error.
+trap "rm -f $tempfile" EXIT SIGTERM ERR
+trap function-name EXIT SIGTERM ERR
+
+# Disable CTRL-C
+trap "" SIGINT
+
+# Re-enable CTRL-C
+trap - SIGINT
+```
+
+## Sources
+
+- [Using Bash traps in your scripts]
+- [The Bash trap command]
+
+[the bash trap command]: https://www.linuxjournal.com/content/bash-trap-command
+[using bash traps in your scripts]: https://opensource.com/article/20/6/bash-trap