exiqgrep: add page (#11565)

* exiqgrep: add page

* exiqgrep: move from `common` to `linux`

* exiqgrep: add display message for bounce count

* exiqgrep: fix formatting

* exiqgrep: update page

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

---------

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/linux/exiqgrep.md

@@ -0,0 +1,28 @@
+# exiqgrep
+
+> The `exiqgrep` utility is a Perl script offering possibilities to `grep` in the Exim queue output.
+> More information: <https://www.exim.org/exim-html-current/doc/html/spec_html/ch-exim_utilities.html>.
+
+- Match the sender address using a case-insensitive search:
+
+`exiqgrep -f '<{{email@somedomain.com}}>'`
+
+- Match the sender address, and display message IDs only:
+
+`exiqgrep -i -f '<{{email@somedomain.com}}>'`
+
+- Match the recipient address:
+
+`exiqgrep -r '{{email@somedomain.com}}'`
+
+- Remove all messages matching the sender address from the queue:
+
+`exiqgrep -i -f '<{{email@somedomain.com}}>' | xargs exim -Mrm`
+
+- Test for bounced messages:
+
+`exiqgrep -f '^<>$'`
+
+- Display the count of bounced messages:
+
+`exiqgrep -c -f '^<>$'`