docs: how to contribute icons

[jeasonstudio]

根据 @LCJove 提供的信息，完善了「如何贡献图标」的文档，以便项目方主动贡献。另外应当增加一个 issue template，当项目方没有贡献能力的情况下可以给我们提需求。

Preview:

• 英文：https://preview-594-ant-design-web3.surge.sh/guide/contribute-icons
• 中文：https://preview-594-ant-design-web3.surge.sh/zh-CN/guide/contribute-icons

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Name	Status	Preview	Comments	Updated (UTC)
ant-design-web3	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 1, 2024 8:31am

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (8731741) to head (b0f0b96).
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[gin-lsl]

还有如何区分分类的也可以说一下，就是在 IconSearch/fields.ts 里面修改一下就可以。