fix: add grayscale colors (neutral palette) to colors.less

[stevula]

[中文版模板 / Chinese template]

🤔 This is a ...

• New feature
• Bug fix
• Site / documentation update
• Demo update
• Component style update
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Internationalization
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?) - this adds Less variables for the grayscale colors mentioned in the docs. They were previously undefined.

🔗 Related issue link

💡 Background and solution

1. The antd docs on color palettes mention a gray palette (source):
   

2. ant-design-colors also includes a gray palette for use within JS (source)

3. The @gray-* variables are undefined in the colors.less (bundled with antd) which causes a compiler error if you try to import them:
   

Solution: added variable definitions for gray colors in colors.less

📝 Changelog

Language	Changelog
🇺🇸 English	Non-breaking change: applications can now import @gray-1 through @gray-10 from the Less theme.
🇨🇳 Chinese	在样式表中定义 @gray-1 ... @gray-10

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed (not needed, docs already mention gray)
• Demo is updated/provided or not needed (not needed)
• TypeScript definition is updated/provided or not needed (no TS changes)
• Changelog is provided or not needed

[github-actions]

[codecov]

Codecov Report

Merging #31129 (a96ee04) into master (399f073) will not change coverage.
The diff coverage is n/a.

❗ Current head a96ee04 differs from pull request most recent head bbd18fc. Consider uploading reports for the commit bbd18fc to get more accurate results

@@            Coverage Diff            @@
##            master    #31129   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          397       397           
  Lines         7561      7570    +9     
  Branches      2074      2134   +60     
=========================================
+ Hits          7561      7570    +9     

Impacted Files	Coverage Δ
components/form/FormItem.tsx	100.00% <0.00%> (ø)
components/dropdown/dropdown-button.tsx	100.00% <0.00%> (ø)
components/table/hooks/useSelection.tsx	100.00% <0.00%> (ø)
components/input/ClearableLabeledInput.tsx	100.00% <0.00%> (ø)
components/table/hooks/useFilter/index.tsx	100.00% <0.00%> (ø)

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[afc163]

ant-design/ant-design-colors#3 (comment)

[stevula]

Updated to use custom neutral/grayscale palette in bbd18fc:

https://ant.design/docs/spec/colors#Neutral-Color-Palette

[stevula]

I have made the changes. Do you need anything else or can you please review again?

[stevula]

@afc163 @PeachScript can you review again please?

[afc163]

@zombieJ 后续统一看看，这是个遗留命名问题，感觉可以下一个大版本统一解决。

[rvinzent]

@afc163 @zombieJ with the next major version (v5.x) now released, is there any reason these changes didn't make it in? what can we do to ensure this feature gap is addressed?

[li-jia-nan]

Conflicting files, I'm sorry to close, can be re initiated if necessary.

[rvinzent]

@li-jia-nan I don't think it's worth putting in the effort to re-open this PR if the maintainers won't commit to merging it, especially since the conflicts in this case would have been trivial to resolve.