feat: implement timestamp callback plugin to show simple timestamp for each header (#8308)

* feat: add community.general.timestamp callback plugin

* feat: add minimal integration tests for timestamp callback plugin

* feat: add maintainers for timestamp callback plugin

* fix: correct license

* fix: remove type annotation for the older python environment

* fix: remove unnecessary comment

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix: add trailing period

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix: split long description into list

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix: remove default and add type

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix; add type

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix: split long description into list

Co-authored-by: Felix Fontein <felix@fontein.de>

* fix: improve description for format_string to describe usable format codes

* fix: clarify the original codes and add copyright from that

* fix: shorten long lines

* fix: correct link format

* fix: add seealso section

* fix: add ignore entries for EOL CI

* fix: update seealso to correctly associate with related plugin

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>

.github/BOTMETA.yml

@@ -91,6 +91,8 @@ files:
     maintainers: ryancurrah
   $callbacks/syslog_json.py:
     maintainers: imjoseangel
+  $callbacks/timestamp.py:
+    maintainers: kurokobo
   $callbacks/unixy.py:
     labels: unixy
     maintainers: akatch