refactor(excel-export): switch to explicit fflate/browser entry

[damyanpetev]

The import from fflate when bundled by vitest with Playwright in Angular project causes this issue:

regardless of component, as long as igniteui-angular is present, because this is bunlded like so:

That's because by default vitest will include the node condition and browser when browser mode is on, but fflate exposes that as import instead so this is bundled:

Note: Can't seem to find a definitive standard on these conditions, this could be resolvable by a fix in the package too.

Alternative:

Tested with the following vitest config:

export default defineConfig({
  // https://vitest.dev/guide/common-errors.html#custom-package-conditions-are-not-resolved
  ssr: {
    resolve: {
      conditions: ['browser', 'import', 'default'],
    },
  },
  resolve: {
    conditions: ['browser', 'import', 'default'],
  },
  test: {
    browser: {
      provider: playwright(),
      enabled: true,
      // at least one instance is required
      instances: [
        { browser: 'chromium' },
      ],
    },
  }
});

But none of those worked, possibly not passed down by the angular process.
The only thing that did work was the alias:

export default defineConfig({
  resolve: {
    alias: [
      { find: /^fflate$/, replacement: 'fflate/browser' },
    ],
  },
  //...

Which might need to be documented if this PR doesn't work out - this needs to be evaluated for SSR scenarios.

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
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• This PR contains breaking changes
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• This PR includes behavioral changes and the feature specification has been updated with them