feat: add env variable to skip binary download on npm install

[jdoubleu]

Description of Change

It adds a simple check for the environment variable ELECTRON_BINARY_SKIP_DOWNLOAD to the postinstall npm script, addressing #16071.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Set the ELECTRON_SKIP_BINARY_DOWNLOAD=1 environment variable to skip electron binary download.

[welcome]

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[MarshallOfSound]

Can we move this after ## Cache

[MarshallOfSound]

Suggested change

	To prevent the binary from being downloaded when you install all npm dependencies just set the environment variable `ELECTRON_BINARY_SKIP_DOWNLOAD`.
	To prevent the binary from being downloaded when you install all npm dependencies you can set the environment variable `ELECTRON_BINARY_SKIP_DOWNLOAD`.

[jdoubleu]

I applied all your requested changes.

[jkleinsc]

Merging as CI failure unrelated to PR.

[release-clerk]

Release Notes Persisted

Set the ELECTRON_SKIP_BINARY_DOWNLOAD=1 environment variable to skip electron binary download.

[welcome]

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