docs: updated webview tag docs to reflect preload behavior with .asar

[iketheguy]

This PR is a documentation update in response to #30656 opened by @Oliver-Fish. It changes the webview tag preload documentation to more accurately reflect the current behavior when referencing asar archives to get the script.

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Release Notes

Notes: docs: updated webview tag documentation to accurately reflect preload behavior with asar archives

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Release Notes Persisted

docs: updated webview tag documentation to accurately reflect preload behavior with asar archives

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I have automatically backported this PR to "14-x-y", please check out #30849

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I have automatically backported this PR to "13-x-y", please check out #30850

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I have automatically backported this PR to "15-x-y", please check out #30851