Automatically set the release date of bundled plugins to match that of DokuWiki

[dregad]

This was originally discussed in https://forum.dokuwiki.org/d/22141-extension-plugin-cli-confused-by-list-command-output.

When listing plugins from CLI using ./bin/plugins.php extension list, the release date for bundled plugins does not match that of the DokuWiki release they are bundled with, as shown in the sample list excerpt below (from a 2024-02-06a Kaos instance), so the date is displayed in red (implying that they are outdated):

acl                  b   2015-07-25   ACL Manager by Andreas Gohr                                                      
authad               bd  2015-07-13   Active Directory Auth Plugin by Andreas Gohr                                     
authldap             bd  2015-07-13   LDAP Auth Plugin by Andreas Gohr                                                 
extension            b   2015-07-26   Extension Manager by Michael Hamann                                              
logviewer            b   2023-12-22   logviewer plugin by Andreas Gohr                                                 
revert               b   2015-07-15   Revert Manager by Andreas Gohr                                                   
styling              b   2020-06-14   styling plugin by Andreas Gohr                                                   
usermanager          b   2015-07-15   User Manager by Chris Smith                                                      

I believe the date in plugin.info.txt file for the bundled plugins should match that of the DokuWiki release they are bundled with (an update to perform when preparing the release).

@andi agreed and requested a modification of the release Github action for that.