feat(exits): add list of exit codes (#74)

Those values are come from /usr/include/sysexits.h

Author: Cj-bc

lib/util/exits.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+#
+# exits
+#
+# Those values are come from /usr/include/sysexits.h
+#
+
+# successful termination
+Util_ExitCode_OK=0
+Util_ExitCode_USAGE=64  # command line usage error
+Util_ExitCode_DATAERR=65  # data format error
+Util_ExitCode_NOINPUT=66  # cannot open input
+Util_ExitCode_NOUSER=67  # addressee unknown
+Util_ExitCode_NOHOST=68  # host name unknown
+Util_ExitCode_UNAVAILABLE=69  # service unavailable
+Util_ExitCode_SOFTWARE=70  # internal software error
+Util_ExitCode_OSERR=71  # system error (e.g., can't fork)
+Util_ExitCode_OSFILE=72  # critical OS file missing
+Util_ExitCode_CANTCREAT=73  # can't create (user) output file
+Util_ExitCode_IOERR=74  # input/output error
+Util_ExitCode_TEMPFAIL=75  # temp failure; user is invited to retry
+Util_ExitCode_PROTOCOL=76  # remote error in protocol
+Util_ExitCode_NOPERM=77  # permission denied
+Util_ExitCode_CONFIG=78  # configuration error