gh-143674: Document F/D complex format characters in struct module

[moneebullah25]

Fixes #143674

Changes

• Added documentation for F (complex from two floats) and D (complex from two doubles) format characters to the struct module docstring

Rationale

These format characters are implemented in the struct module (lines 858-859, 1189-1190, 1504-1505 in Modules/_struct.c) but were missing from the module's docstring documentation. Users consulting the docstring with help(struct) would not know these options exist.

Testing

• Verified that F and D format characters are implemented in the code
• Confirmed the docstring change follows the existing format and style
• The change is minimal and only adds missing documentation

Checklist

• Minimal change - only added missing documentation
• Followed existing docstring format and style
• Commit message follows CPython guidelines

• Issue: Struct module docstring lacks format characters for complex types (F/D) #143674

[skirpichev]

Are you using generative AI for this pr?

[moneebullah25]

Are you using generative AI for this pr?

Yep I use it for commit message and comment

[hugovk]

Reported @quanghuynh10111-lab to GitHub.

[miss-islington-app]

Thanks @moneebullah25 for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-143918 is a backport of this pull request to the 3.14 branch.

[vstinner]

Merged, thank you.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x (tier-2) has failed when building commit 3e93225.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/725/builds/12571) and take a look at the build logs.
4. Check if the failure is related to this commit (3e93225) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/725/builds/12571

Failed tests:

• test_urllib2net

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 4, done.        
remote: Counting objects:  25% (1/4)        
remote: Counting objects:  50% (2/4)        
remote: Counting objects:  75% (3/4)        
remote: Counting objects: 100% (4/4)        
remote: Counting objects: 100% (4/4), done.        
remote: Compressing objects:  25% (1/4)        
remote: Compressing objects:  50% (2/4)        
remote: Compressing objects:  75% (3/4)        
remote: Compressing objects: 100% (4/4)        
remote: Compressing objects: 100% (4/4), done.        
remote: Total 4 (delta 0), reused 3 (delta 0), pack-reused 0 (from 0)        
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HEAD is now at 3e932257980 gh-143674: Document F/D complex format characters in struct module (#143675)
Switched to and reset branch 'main'

make: *** [buildbottest] Error 2