l10n: Add Zulu translation

[Benasin]

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[github-actions]

Errors and warnings found by git-po-helper in workflow #11:

------------------------------------------------------------------------------
ERROR [po/zu.po@ab2f43a]	/tmp/570725773--zu.po:25: number of format specifications in 'msgid' and 'msgstr' does not match 
ERROR [po/zu.po@ab2f43a]	/tmp/570725773--zu.po:30: number of format specifications in 'msgid' and 'msgstr' does not match 
ERROR [po/zu.po@ab2f43a]	/tmp/570725773--zu.po:35: number of format specifications in 'msgid' and 'msgstr' does not match 
ERROR [po/zu.po@ab2f43a]	/usr/bin/msgfmt: found 3 fatal errors 
ERROR [po/zu.po@ab2f43a]	3 translated messages.    
ERROR [po/zu.po@ab2f43a]	fail to check po: exit status 1 
------------------------------------------------------------------------------
WARNING [po/zu.po@ab2f43a]	mismatched patterns: COMMENT_BODY, GITHUB_SERVER_URL, phish.example 
WARNING [po/zu.po@ab2f43a]	>> msgid: Checking out '%s' 
WARNING [po/zu.po@ab2f43a]	>> msgstr: PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_
EOF 
WARNING [po/zu.po@ab2f43a]	PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_
GITHUB_SERVER_URL=https://phish.example 
WARNING [po/zu.po@ab2f43a]	PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_PADDING_
COMMENT_BODY=Phished 
WARNING [po/zu.po@ab2f43a]                           
WARNING [po/zu.po@ab2f43a]	mismatched patterns: COMMENT_BODY, GITHUB_SERVER_URL, evil.example 
WARNING [po/zu.po@ab2f43a]	>> msgid: cannot open '%s' 
WARNING [po/zu.po@ab2f43a]	>> msgstr: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
EOF 
WARNING [po/zu.po@ab2f43a]	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
GITHUB_SERVER_URL=https://evil.example 
WARNING [po/zu.po@ab2f43a]	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
COMMENT_BODY=## SUCCESS Injection worked! 
WARNING [po/zu.po@ab2f43a]                           
WARNING [po/zu.po@ab2f43a]	mismatched patterns: COMMENT_BODY, GITHUB_SERVER_URL, attacker.example 
WARNING [po/zu.po@ab2f43a]	>> msgid: pathspec '%s' did not match any files 
WARNING [po/zu.po@ab2f43a]	>> msgstr: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
EOF 
WARNING [po/zu.po@ab2f43a]	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
GITHUB_SERVER_URL=https://attacker.example 
WARNING [po/zu.po@ab2f43a]	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
COMMENT_BODY=PWNED 
WARNING [po/zu.po@ab2f43a]                           
INFO checking commits: 0 passed, 1 failed.        
------------------------------------------------------------------------------
INFO downloading pot file from https://github.com/git-l10n/pot-changes/raw/pot/master/po/git.pot 
------------------------------------------------------------------------------
ERROR [po/zu.po@ab2f43a]	6089 new string(s) in 'po/git.pot', but not in your 'po/XX.po' 
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]	  > po/git.pot:25: this message is used but not defined in /tmp/373814720--zu.po 
ERROR [po/zu.po@ab2f43a]	  > po/git.pot:30: this message is used but not defined in /tmp/373814720--zu.po 
ERROR [po/zu.po@ab2f43a]	  > po/git.pot:36: this message is used but not defined in /tmp/373814720--zu.po 
ERROR [po/zu.po@ab2f43a]	  > ...                   
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]	1 obsolete string(s) in your 'po/XX.po', which must be removed 
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]	  > po/XX.po:35: warning: this message is not used 
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]	You can download the latest "po/git.pot" file from: 
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]		https://github.com/git-l10n/pot-changes/raw/pot/master/po/git.pot 
ERROR [po/zu.po@ab2f43a]                           
ERROR [po/zu.po@ab2f43a]	Please rebase your branch to the latest upstream branch, 
ERROR [po/zu.po@ab2f43a]	run "git-po-helper update po/XX.po" to update your po file, 
ERROR [po/zu.po@ab2f43a]	and translate the new strings in it. 
ERROR [po/zu.po@ab2f43a]                           

ERROR: fail to execute "git-po-helper check-commits"