fix(language-plugin-pug): compute offset correctly of pug class

[KazariEX]

fix #1767

[KazariEX]

It should be noted that this currently only applies to cases where classnames are completely consecutive. Due to the code parsing logic, it cannot obtain the source offset for each class. I'm trying to find a solution.

[pkg-pr-new[bot]]

commit: cb5d5a6

vue-component-meta

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-meta@4652 ```

vue-component-type-helpers

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-type-helpers@4652 ```

@vue/language-core

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-core@4652 ```

@vue/language-plugin-pug

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-plugin-pug@4652 ```

@vue/language-server

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-server@4652 ```

@vue/language-service

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-service@4652 ```

vue-tsc

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-tsc@4652 ```

@vue/typescript-plugin

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/typescript-plugin@4652 ```

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[johnsoncodehk]

Thanks for looking into this!