fix(loader): support @charset removing and @import without url()

[yanni4night]

PR Details

• 支持无url()的@import语句
• 移除@charset语句
• 更新了匹配url()的正则

Description

1. 将无url()的@import语句转换为有url()，以供后续统一处理；
2. @charset在<style>无意义，直接移除；
3. url()可匹配带文件名带括号的资源

Related Issue

#446

Motivation and Context

1. 支持了无url()的@import语句，兼容性更好
2. 顺带移除了可能出现的@charset语句，减少控制台warning
3. 优化了url()匹配模式，能兼容更多合理的资源名

How Has This Been Tested

repo中无相关test case，可手动在 https://github.com/yanni4night/garfish-issue-reproduction/tree/issue-446 验证。

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[imtaotao]

@import 的支持可以先不用，因为 import 进来的 css 文件里面可能还需要处理，里面的路径还需要修正

[codecov]

Codecov Report

Merging #453 (7c309c6) into main (b742a2d) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #453      +/-   ##
==========================================
+ Coverage   78.70%   78.83%   +0.12%     
==========================================
  Files          84       84              
  Lines       10791    10795       +4     
  Branches     1502     1509       +7     
==========================================
+ Hits         8493     8510      +17     
+ Misses       2290     2277      -13     
  Partials        8        8              

Impacted Files	Coverage Δ
packages/loader/src/managers/style.ts	65.67% <100.00%> (+24.68%)	⬆️
packages/browser-vm/src/modules/uiEvent.ts	100.00% <0.00%> (ø)

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[yanni4night]

@import 的支持可以先不用，因为 import 进来的 css 文件里面可能还需要处理，里面的路径还需要修正

应该能应付绝大多数情况，e.g. 被import进来的box.css的路径被修正后，其里面的相对引用也是自动纠正的。

<!-- main.html -->
<div __garfishmockhtml__="">
   <div __garfishmockhead__="">
        <style type="text/css">
          @import url("http://localhost:9000/box.css");
       </style>
    </div>
</div>

/* box.css */
@import "./size.css";

.box {
  background: url(./bg.jpg);
}

[imtaotao]

@import 的支持可以先不用，因为 import 进来的 css 文件里面可能还需要处理，里面的路径还需要修正

应该能应付绝大多数情况，e.g. 被import进来的box.css的路径被修正后，其里面的相对引用也是自动纠正的。

<!-- main.html -->
<div __garfishmockhtml__="">
   <div __garfishmockhead__="">
        <style type="text/css">
          @import url("http://localhost:9000/box.css");
       </style>
    </div>
</div>

/* box.css */
@import "./size.css";

.box {
  background: url(./bg.jpg);
}

可以针对这些场景，补充一些测试用例