fix(patches): enable electron sandbox

[rxri]

The electron sandbox disables the node integration within the renderer process. However, the custom-gallery patch required the use of the require() function, causing the renderer to fail loading within the sandbox. To resolve this issue, the function that requires user's product.json has been moved to main.js, and the user's product.json is now assigned to global scope which can be used in product.ts.

Fixes #1482
This patch works on stable (1.78.2) and insider (1.79.0) versions

[daiyam]

@rxri Thanks a lot

[daiyam]

The issue with git apply was due to merge-user-product.patch being a bit corrupted (the space were missing, mostly due to the setting Files: Trim Trailing Whitespace enabled).
To avoid that issue, in .editorconfig, the behaviour has been disabled for those files. (EditorConfig for VS Code needs to be installed)